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segunda-feira, 30 de junho de 2014

Extraindo o gás do folhelho de Utica

Extraindo o gás do folhelho de Utica
Até poucos anos atrás o folhelho de Utica, em Ohio, era simplesmente desprezado pelos pesquisadores. Nos últimos três anos tudo mudou e esta rocha tornou-se um dos mais valiosos alvos para óleo e gás em toda a América do Norte.

O folhelho de Utica é um sedimento, de idade Ordoviciana, fino, escuro, com materiais orgânicos e calcários intercalados (foto).

Assim que os geólogos perceberam a sua importância começou a sondagem.

Na primeira etapa centenas de furos verticais foram realizados (mapa 1) ao longo de uma malha cuidadosamente planejada.

O que não se percebe na superfície é que para cada furo vertical existem até 8 furos horizontais de 3.000m de comprimento que são perfurados a partir do vertical (mapa 2, da projeção horizontal). É através dos furos horizontais, que estão inseridos no folhelho alvo (ou xisto como essas rochas são chamadas erroneamente no Brasil), que é feito o processo de faturamento hidráulico que permite a extração do gás e óleo dessas rochas: o fracking. Os furos horizontais são perfurados em um padrão que permite a extração, praticamente total, do gás e óleo contido no folhelho.

O processo de extração, o fracking é razoavelmente simples. Ele consiste na injeção de água com areia em altíssima pressão de forma a causar fraturamentos e espaços abertos no folhelho que são preenchidos pela areia. Esse processo causa uma maior porosidade e permeabilidade  da rocha por onde o gás é extraído juntamente com os demais hidrocarbonetos.

O método transformou a indústria e permitiu aos Estados Unidos uma verdadeira revolução energética extraindo gás e óleo em rochas antes inacessíveis e consideradas estéreis. A revolução do fracking é tão grande que está tornando os Estados Unidos, que era o maior importador de óleo e gás do mundo, em um grande exportador.

Tudo isso em pouco mais de uma década.

Apesar do fracking ter reduzido os custos do gás, empregado centenas de milhares de pessoas e revolucionado a indústria da maior economia do mundo ele tem forte oposição.

Vários grupos ambientalistas combatem o fracking dizendo que o método usa imensas quantidades de água (mais de 5 milhões de litros por furo) onde são misturados produtos químicos que podem contaminar a água dos aquíferos superficiais. Vários estudos foram feitos nos Estados Unidos onde existem dezenas de milhares de sondagens com o uso de fracking e está sendo comprovado que a poluição pode ser evitada e quando ocorre é por erros humanos e não do método.

No momento está sendo finalizado um estudo contratado pelo Congresso Americano, a quatro anos atrás, para determinar o real impacto do fracking sobre os recursos de água. Mas o que mais assusta os ambientalistas é o enorme sucesso do fracking. Ele está viabilizando a extração de gás e óleo em um momento em que essas fontes de energia deveriam estar sendo substituídas por outras mais limpas.

É que os ambientalistas querem simplesmente acabar com os combustíveis fósseis e o fracking é a grande barreira que está revitalizando a indústria do gás e óleo.

Trata-se de um impasse interessante e cruel.

De um lado alguns países ricos que podem realmente investir em fontes alternativas de energia, mais caras e menos eficientes e, do outro, os países pobres onde as necessidades são tão básicas quanto um prato de comida.

Como negar a esses a revolução energética que irá criar milhões de empregos e mudar a economia de suas nações enfraquecidas?

Por mais que queiramos o mundo ainda é composto por regiões ricas e outras, a maioria, onde impera a miséria, o genocídio e o descaso ao ser humano. Essas regiões pobres precisam urgentemente de uma verdadeira revolução econômica e social que permita o fortalecimento de suas economias com a criação de novos empregos. Em todas essas regiões existem grandes recursos inexplorados de folhelhos que poderiam estar gerando energia e alimentando a economia local.

Enquanto isso nos Estados Unidos o fracking adicionou 100 anos de recursos de gás e óleo às reservas do país ao mesmo tempo em que substitui as emissões vindas da queima do carvão.


Megasiderúrgica chinesa começará produção em 2015

Megasiderúrgica chinesa começará produção em 2015
Apesar dos problemas do mercado atual e do desequilíbrio entre a oferta e a procura a Baosteel, a maior siderúrgica chinesa, mantém o projeto Zhanjiang  como planejado. Trata-se de uma gigantesca planta metalúrgica com capacidade para 10 milhões de toneladas de aço por ano. O projeto foi aprovado pela Comissão Nacional de Desenvolvimento e Reforma chinesa e irá começar a produzir no final de 2015. Esta planta suprirá a necessidade das indústrias de ponta que usam aços de alta qualidade, raros na China.

O novo aço de Zhanjiang  irá substituir o aço das siderúrgicas obsoletas e caras que estão sendo fechadas em toda a China. Até o momento o país deixou de produzir 11,65 milhões de toneladas de aço cru vindo dessas plantas.  Ao todo a China deverá eliminar 17 milhões de toneladas de aço produzido em siderúrgicas antiquadas.

Lulo a mais nova mina de Angola promete eclipsar Catoca

Lulo a mais nova mina de Angola promete eclipsar Catoca
A mina de diamante sobre o kimberlito de Catoca é uma das grandes geradoras de renda em Angola. Mas, segundo notícias recentes, Catoca estará sendo deslocada para o segundo lugar.

O novo nome a ser lembrado é Lulo. Lulo é um projeto cuja produção de diamantes é esperada para 2016. Segundo o relatório publicado recentemente, Lulo será o maior produtor de diamantes do país e seus diamantes irão valer mais de dez vezes o valor médio de Catoca...

Se isso for verdade Angola passará em breve a ser uma das maiores produtoras de diamantes do mundo. 

A concessão que engloba os alvos tipo Lulo, de 3.000km2, pertence a Lucapa Diamonds Company ltd e cobre uma região onde ocorrem os maiores depósitos aluvionares de diamante da Angola: a bacia do Rio Cuango.

Lulo é um kimberlito descoberto pelo levantamento aerogeofísico feito em 2008. O kimberlito está localizado no Graben de Lucapa onde a maioria dos kimberlitos angolanos ocorrem. Esses pipes foram preservados pelas areias do Deserto do Kalahari e, consequentemente, não estão muito erodidos.

Os aluviões da área já produziram grandes pedras, de até 131,4 quilates, e as vendas dos diamantes de Lulo foram realizadas com preços superiores a US$6.000/quilate, uma verdadeira anomalia. Em Catoca o preço médio do quilate é de US$100,00.

domingo, 29 de junho de 2014

Amerix busca sócio ou comprador para projeto de ouro no Brasil

Amerix busca sócio ou comprador para projeto de ouro no Brasil




A Amerix Precious Metals vai rever as alternativas estratégicas, com o objetivo de agregar valor aos seus acionistas. Como parte do processo, a empresa analisará a possibilidade de joint ventures, fusões, aquisições e até a venda da companhia, ou outros acordos corporativos que gerem valor para o acionista. A informação consta de comunicado enviado hoje ao mercado.
Segundo o comunicado, a Amerix iniciou conversas e mantém acordos de confidencialidade com uma série de interessados. Não há uma data para encerrar a revisão ou garantias de que qualquer transação seja efetuada. De acordo com a companhia, não há intenção de divulgar mais detalhes sobre a análise de alternativas estratégicas, até que o Conselho de Administração aprove uma transação específica.

Projeto de ouro Limão, no ParáA Amerix é uma empresa de Ontário, no Canadá, que explora metais preciosos no Brasil. A companhia visa a valorização de seus acionistas por meio da expansão dos recursos do ouro em suas propriedades. O Brasil tem um potencial significativo para exploração do metal e é comprovadamente um país com condições favoráveis à mineração. O objetivo da empresa é continuar a busca por propriedades de exploração no país, por meio de aquisição ou fusão.

No Brasil, a Amerix atua há mais de 10 anos, com operações na mina de ouro Limão, no Estado do Pará, que está situada na Província Aurífera dos Tapajós, considerada uma das regiões mais importantes da exploração do ouro no país e principal fonte do metal entre os anos 1970 e 1990.

Recentemente, a Amerix adquiriu as concessões de exploração de Serra Dourada, que está posicionada ao lado oeste da mina Limão, resultando em 18 mil hectares com potencial de exploração.

Em 2012, a Amerix iniciou os programas de sondagem na mina de Limão, com resultados promissores. A exploração das concessões Limão e Serra Dourada continuam a desenvolver novas metas para sondagens futuras.

As ações da Companhia são negociadas na TSX Venture Exchange e na Frankfurt Stock Exchange.

Ouro Roxo disputa jazidas de ouro com garimpeiros no Pará

Ouro Roxo disputa jazidas de ouro com garimpeiros no Pará



A localidade de São José, que fica às margens do rio Pacu, em Jacareacanga no sudoeste do Pará, está no centro de uma disputa entre garimpeiros e a companhia Ouro Roxo Participações pelas jazidas de ouro da região. A empresa, que tem como sócio uma pessoa com 200 permissões de garimpo, reivindica o direito de exploração do local e afirma que a produção do minério é inacessível pelos métodos artesanais.
Mapa de Jacareacanga, no Pará. Crédito: Google EarthEm 2009, a Ouro Roxo Participações, que tem como acionista majoritário o grupo de mineração canadense Albrook Gold Corporation, garantiu os direitos de exploração do subsolo do garimpo Paxiúba, no Pará, por meio da Mineradora Ouro Roxo, onde garimpeiros ainda extraem ouro com métodos tradicionais.

A mineradora Ouro Roxo tem uma autorização de pesquisa 852678/1993 no município de Jacareacanga (PA), com 3,7 mil hectares, que antes pertencia à Mineração Vila Porto Rico. Nesse município, que tem 53 mil quilômetros quadrados, um pouco menor que a Croácia, está também o garimpo São José.

Segundo os registros do DNPM, os detentores desses direitos registram denúncias de invasão em 2007 e 2008 e recentemente, em abril e em junho do ano passado.

Dirceu Santos Frederico Sobrinho, representantes da Planalto S.A. e sócio na Ouro Roxo Participações, detém cerca de 200 permissões de lavra garimpeira nos municípios de Itaituba e Jacareacanga, ambos no Pará, segundo dados do DNPM e do sistema IntierraRMG.

Em março de 2010, a Polícia Federal e autoridades do governo chegaram a ordenar a saída dos garimpeiros. Após uma resistência inicial, eles deixaram o local, mas argumentaram que suas famílias haviam vivido na região por mais de meio século e durante este tempo haviam adquirido direitos sobre a terra.

Segundo o líder garimpeiro, José Gilmar de Araújo, desde então, o grupo foi se esforçando para obter a legalização de suas atividades de mineração, com pedido formal enviado à Brasília. “Mas não estamos chegando a lugar nenhum”, disse ele à BBC.

Depois da expulsão em 2010, os garimpeiros tentaram por três anos obter a permissão para voltar ao garimpo Paxiúba. Em 12 de junho de 2013, assumiram a responsabilidade e reocuparam o local por conta própria.

"Nós colocamos todo o nosso dinheiro na atividade. Vamos ficar arruinados se não pudermos produzir ouro", afirmou Araújo.

Enquanto isso, a Ouro Roxo está perdendo dinheiro e demonstra insatisfação com a situação. “Se eles permanecerem lá, vão tornar o projeto todo inviável para nós, por conta do dano que estão causando. Os garimpeiros não se desenvolvem. Eles estão presos em uma cultura de pobreza, a prostituição, as drogas", afirmou Dirceu Santos Frederico Sobrinho, acionista brasileiro da empresa.

De acordo com o advogado dos garimpeiros, Antonio João Brito Alves, o conflito está aumentando. Ele disse que Sobrinho ameaçou sua família, dizendo que iriam "sofrer as consequências", caso ele não desistisse do caso. Mas o acionista nega veementemente ter ameaçado Brito Alves.

As consequências deste conflito pode ter implicações mais amplas. Se os garimpeiros ganharem a disputa, ou receberem compensação para sair da mina, outras comunidades de garimpeiros estão susceptíveis de vir a frente com a mesma demanda. Com isso, a pequena aldeia de São José tornou-se um caso de teste improvável para uma batalha mais ampla para os direitos dos garimpeiros.

De acordo com moradores do povoado, São José não é hoje tão movimentado como era antes. Nas décadas passadas, a violência era marca registrada do local. “Quando cheguei aqui , em 1986, alguém era morto a tiros quase todos os dias" , afirmou Ozimar Alves de Jesus, comerciante da região.

Para o garimpeiro José de Alencar, atualmente, São José é um lugar muito tranquilo, o principal problema para os trabalhadores da região é a incerteza sobre o futuro da própria mina e o poder que as mineradoras possuem. "Uma grande empresa chega e as portas estão sempre abertas para ela. Parece que há uma lei para as grandes empresas e outra para nós", disse.

A descoberta do ouro na bacia do rio Tapajós, em 1958, atraiu dezenas de milhares de garimpeiros ao local. Apesar de a atividade ter diminuído nos últimos anos, muitos homens ainda trabalham de forma primitiva em minas de ouro ainda não cadastradas. Além da Ouro Roxo, empresas como Belo Sun e BBX possuem operações e projetos de extração de ouro na região.

TriStar começa terceira fase de sondagem em Castelo dos Sonhos

TriStar começa terceira fase de sondagem em Castelo dos Sonhos




A TriStar Gold deu início hoje (1) à terceira fase da campanha de sondagem no projeto de ouro Castelo dos Sonhos, no Pará. O objetivo da mineradora júnior canadense é investigar o alvo Esperança South. A TriStar pretende finalizar até agosto deste ano a documentação necessária para solicitar a conversão da autorização de pesquisa da área em concessão de lavra.
De acordo com a mineradora, a campanha de sondagem em 2014 vai estabelecer parâmetros para fortalecer os dados do relatório técnico de estimativa de recursos, que deve ser encaminhado ao Departamento Nacional de Produção Mineral (DNPM).
Vista aérea do projeto Castelo dos Sonhos
As sondagens pretendem identificar se há continuação da mineralização de Esperança South. Segundo a TriStar, à medida que os resultados forem divulgados pelos laboratórios, novas áreas de interesse podem passar por sondagem.

A mineradora canadense informou que concluiu a segunda e última parcela (tranche) da emissão privada anunciada em 16 de janeiro deste ano. A TriStar levantou US$ 2,2 milhões com a emissão de 22,3 milhões de títulos, que são compostos por uma ação da empresa e uma opção de compra (warrant).

Todas as ações, incluindo as que foram adquiridas por meio de warrants no segundo tranche, estão sujeitas a um prazo de carência de até 29 de julho de 2014.

A TriStar informou, em 5 de fevereiro, que fez um aditivo ao contrato de compra de Castelo de Sonhos, para estender as datas de vencimento referentes às parcelas restantes para a compra da propriedade. Os prazos para pagar parte dos cerca de US$ 1,7 milhão foram prorrogados para 2015.

Uma parcela de US$ 300 mil que deveria ser paga no último mês de março foi dividida em três pagamentos de US$ 100 mil nos próximos onze meses. A primeira parte estava prevista para ser paga até 13 de março. O pagamento final de US$ 1,4 milhão, que estava previsto para setembro deste ano, foi adiado para julho do ano que vem. Porém, serão cobrados US$ 75 mil de juros pelo atraso.

A TriStar Gold é uma empresa de exploração de ouro com ênfase para propriedades de alto potencial, em especial no Brasil. Seus principais projetos são Castelo de Sonhos e Bom Jardim, ambos na província mineral de Tapajós, no Estado do Pará.

Produção da AngloGold Ashanti tem melhor desempenho dos últimos 4 anos

Produção da AngloGold Ashanti tem melhor desempenho dos últimos 4 anos



A AngloGold Ashanti aumentou a produção para 1,06 milhão de onças de ouro no primeiro trimestre deste ano, volume 17% acima das 899 mil onças produzidas nos três primeiros meses de 2013. Segundo relatório de resultados trimestrais, divulgado hoje (19), foi o melhor desempenho registrado, durante o mesmo período, dos últimos quatro anos. No Brasil, a empresa produziu um total de 126 mil onças.
De acordo com a mineradora, os custos de produção total também foram reduzidos, em 22%, na mesma comparação anual. A Anglo afirmou que tanto os números de produção quanto os custos bateram as previsões da empresa para o período, “à medida que as performances operacionais e as iniciativas de custo estão reposicionando os negócios da companhia”.

"Nossos operadores entregaram uma outra previsão, agora mais forte, e nós continuaremos a gerir os custos de forma agressiva. Ainda há muito trabalho a fazer, mas continuamos focados em continuar a produzir resultados positivos para os nossos acionistas, em condições de mercado difíceis", disse o CEO da empresa, Srinivasan Venkatakrishnan.

No Brasil, a produção da AngloGold Ashanti Mineração foi de 94 mil onças de ouro, a um custo total de US$ 619/oz, resultado positivo, se comparado as 92 mil onças produzidas a US$ 689/oz no mesmo período no ano passado. Já a unidade de negócios Serra Grande, em Goiás, produziu 32 mil onças, a um custo de US$ 799 por onça.

Na mina de Cuiabá, em Sabará (MG), que faz parte do complexo AngloGold Ashanti Mineração, maiores teores ajudaram a compensar taxas de produção inferiores, devido às interrupções após um acidente fatal na mina.

O custo de produção total das operações da Anglo, que inclui despesas de capital e custos de exploração, diminuiu 22% chegando a US$ 993 por onça produzida. Segundo a mineradora, os resultados positivos foram conquistados através do ramp up de novas minas de baixo custo, Kibali, na República Democrática do Congo, e Tropicana, na Austrália.

De acordo o relatório, ao longo dos últimos 18 meses, a AngloGold Ashanti tem dado passos decisivos para se adaptar à queda acentuada no preço do ouro e as condições mais voláteis de mercado.

“Com a redução nos custos corporativos e de exploração, a empresa está no caminho certo para atingir sua meta de redução de US$ 500 milhões nos custos de operação até o final deste ano”, afirma o documento. Para isso, a empresa continua a investir na expansão da mina Cripple Creek & Victor, nos EUA, e estendendo a vida útil da mina Mponeng, na África do Sul.

No relatório, a mineradora aponta três fatalidades em suas operações durante os três primeiros meses do ano, incluindo a morte de dois empregados contratados na mina de Cuiabá, em Sabará (MG). A outra vítima fatal foi registrada no Projeto Mponeng, na África do Sul.

Segundo a Anglo, a empresa continua empenhada em eliminar acidentes em suas minas através de intervenções de segurança que, no ano passado, resultaram em uma redução de 50% nos incidentes fatais. A mineradora afirmou que a taxa de lesões do primeiro trimestre deste ano é a melhor registrada na história da empresa.

A dívida líquida da mineradora foi para US$ 3,095 bilhões, uma pequena redução que aponta
um fluxo de caixa positivo. "Dada as incertezas do preço do ouro no mercado, continuamos focados em nossa flexibilidade financeira. Os níveis de endividamento e taxas de juros continuam altas em relação aos níveis históricos, mas fizemos um bom progresso diversificando nossas fontes de financiamento”, afirmou o CFO da empresa, Richard Duffy.

No Brasil, a AngloGold tem, em Sabará (MG), as minas Cuiabá e Lamego e, em Santa Bárbara (MG), a operação da Mina Córrego do Sítio.
Mina de ouro Cuiabá, em Sabará (MG).

Ouro tem preço estável durante a semana

Ouro tem preço estável durante a semana

O preço do ouro no mercado à vista se manteve próximo a US$ 1.320 por onça troy nos ultimos sete dias. Veja o gráfico.

Preço do ouro no mercado à vista (em USD por onça troy).

Diamond

Diamond


This article is about the mineral. For the gemstone, see Diamond (gemstone). For other uses, including the shape , see Diamond (disambiguation).
Diamond
A clear octahedral stone protrudes from a black rock.
The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. Its lustrous faces also indicate that this crystal is from a primary deposit.
General
Category Native Minerals
Formula
(repeating unit)
C
Strunz classification 01.CB.10a
Identification
Formula mass 12.01 g⋅mol−1
Color Typically yellow, brown or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple and red.
Crystal habit Octahedral
Crystal system Isometric-Hexoctahedral (Cubic)
Cleavage 111 (perfect in four directions)
Fracture Conchoidal (shell-like)
Mohs scale hardness 10
Luster Adamantine
Streak Colorless
Diaphaneity Transparent to subtransparent to translucent
Specific gravity 3.52±0.01
Density 3.5–3.53 g/cm3
Polish luster Adamantine
Optical properties Isotropic
Refractive index 2.418 (at 500 nm)
Birefringence None
Pleochroism None
Dispersion 0.044
Melting point Pressure dependent
References [1][2]
In mineralogy, diamond (from the ancient Greek αδάμας – adámas "unbreakable") is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at standard conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells.
Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boron and nitrogen. Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green (radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical dispersion (ability to disperse light of different colors).
Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 118 mi) in the Earth's mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years (25% to 75% of the age of the Earth). Diamonds are brought close to the Earth′s surface through deep volcanic eruptions by a magma, which cools into igneous rocks known as kimberlites and lamproites. Diamonds can also be produced synthetically in a high-pressure high-temperature process which approximately simulates the conditions in the Earth's mantle. An alternative, and completely different growth technique is chemical vapor deposition (CVD). Several non-diamond materials, which include cubic zirconia and silicon carbide and are often called diamond simulants, resemble diamond in appearance and many properties. Special gemological techniques have been developed to distinguish natural and synthetic diamonds and diamond simulants.

History

The name diamond is derived from the ancient Greek αδάμας (adámas), "proper", "unalterable", "unbreakable", "untamed", from ἀ- (a-), "un-" + δαμάω (damáō), "I overpower", "I tame".[3] Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could be found many centuries ago along the rivers Penner, Krishna and Godavari. Diamonds have been known in India for at least 3,000 years but most likely 6,000 years.[4]
Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history.[5][6] The popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns.[7]
In 1772, Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond is composed of carbon.[8] Later in 1797, Smithson Tennant repeated and expanded that experiment.[9] By demonstrating that burning diamond and graphite releases the same amount of gas he established the chemical equivalence of these substances.[10]
The most familiar use of diamonds today is as gemstones used for adornment, a use which dates back into antiquity. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds: these are carat, cut, color, and clarity.[11] A large, flawless diamond is known as a paragon.

Natural history

The formation of natural diamond requires very specific conditions—exposure of carbon-bearing materials to high pressure, ranging approximately between 45 and 60 kilobars (4.5 and 6 GPa), but at a comparatively low temperature range between approximately 900 and 1,300 °C (1,650 and 2,370 °F). These conditions are met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike.[12]

Formation in cratons

A triangular facet of a crystal having triangular etch pits with the largest having a base length of about 0.2 millimetres (0.0079 in)
One face of an uncut octahedral diamond, showing trigons (of positive and negative relief) formed by natural chemical etching
The conditions for diamond formation to happen in the lithospheric mantle occur at considerable depth corresponding to the requirements of temperature and pressure. These depths are estimated between 140 and 190 kilometers (87 and 118 mi) though occasionally diamonds have crystallized at depths about 300 kilometers (190 mi).[13] The rate at which temperature changes with increasing depth into the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates the temperature rises more quickly with depth, beyond the range required for diamond formation at the depth required. The correct combination of temperature and pressure is only found in the thick, ancient, and stable parts of continental plates where regions of lithosphere known as cratons exist. Long residence in the cratonic lithosphere allows diamond crystals to grow larger.[13]
Through studies of carbon isotope ratios (similar to the methodology used in carbon dating, except with the stable isotopes C-12 and C-13), it has been shown that the carbon found in diamonds comes from both inorganic and organic sources. Some diamonds, known as harzburgitic, are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon from organic detritus that has been pushed down from the surface of the Earth's crust through subduction (see plate tectonics) before transforming into diamond. These two different source of carbon have measurably different 13C:12C ratios. Diamonds that have come to the Earth's surface are generally quite old, ranging from under 1 billion to 3.3 billion years old. This is 22% to 73% of the age of the Earth.[13]
Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles. As diamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube, octahedron, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can have rounded off and unexpressive edges and can be elongated. Sometimes they are found grown together or form double "twinned" crystals at the surfaces of the octahedron. These different shapes and habits of some diamonds result from differing external circumstances. Diamonds (especially those with rounded crystal faces) are commonly found coated in nyf, an opaque gum-like skin.[14]

Space diamonds

Primitive interstellar meteorites were found to contain carbon possibly in the form of diamond (Lewis et al. 1987).[15] Not all diamonds found on Earth originated here. A type of diamond called carbonado that is found in South America and Africa may have been deposited there via an asteroid impact (not formed from the impact) about 3 billion years ago. These diamonds may have formed in the intrastellar environment, but as of 2008, there was no scientific consensus on how carbonado diamonds originated.[16][17]
Diamonds can also form under other naturally occurring high-pressure conditions. Very small diamonds of micrometer and nanometer sizes, known as microdiamonds or nanodiamonds respectively, have been found in meteorite impact craters. Such impact events create shock zones of high pressure and temperature suitable for diamond formation. Impact-type microdiamonds can be used as an indicator of ancient impact craters.[12] Popigai crater in Russia may have the world's largest diamond deposit, estimated at trillions of carats, and formed by an asteroid impact.[18]
Scientific evidence indicates that white dwarf stars have a core of crystallized carbon and oxygen nuclei. The largest of these found in the universe so far, BPM 37093, is located 50 light-years (4.7×1014 km) away in the constellation Centaurus. A news release from the Harvard-Smithsonian Center for Astrophysics described the 2,500-mile (4,000 km)-wide stellar core as a diamond.[19] It was referred to as Lucy, after the Beatles' song "Lucy in the Sky With Diamonds".[20][21]

Transport from mantle

Schematic cross section of an underground region 3 km deep and 2 km wide. A red dike stretches across the bottom, and a pipe containing some xenoliths runs from the dike to the surface, varying from red at the bottom to orange-yellow at the top. The pipe's root, at its bottom, is about 1 km long, and its diatreme, above the root, is about 1.5 km long. The pipe's top is a crater, rimmed by a tuff ring and containing washed-back ejecta. The erosion level is almost zero for Orapa, about 1 km for Jagersfontein, and about 1.4 km for Kimberley.
Schematic diagram of a volcanic pipe
Diamond-bearing rock is carried from the mantle to the Earth's surface by deep-origin volcanic eruptions. The magma for such a volcano must originate at a depth where diamonds can be formed[13]—150 km (93 mi) or more (three times or more the depth of source magma for most volcanoes). This is a relatively rare occurrence. These typically small surface volcanic craters extend downward in formations known as volcanic pipes.[13] The pipes contain material that was transported toward the surface by volcanic action, but was not ejected before the volcanic activity ceased. During eruption these pipes are open to the surface, resulting in open circulation; many xenoliths of surface rock and even wood and fossils are found in volcanic pipes. Diamond-bearing volcanic pipes are closely related to the oldest, coolest regions of continental crust (cratons). This is because cratons are very thick, and their lithospheric mantle extends to great enough depth that diamonds are stable. Not all pipes contain diamonds, and even fewer contain enough diamonds to make mining economically viable.[13] Diamonds are very rare[22] because most of the crust is too thin to permit diamond crystallization, whereas most of the mantle has relatively little carbon.
The magma in volcanic pipes is usually one of two characteristic types, which cool into igneous rock known as either kimberlite or lamproite.[13] The magma itself does not contain diamond; instead, it acts as an elevator that carries deep-formed rocks (xenoliths), minerals (xenocrysts), and fluids upward. These rocks are characteristically rich in magnesium-bearing olivine, pyroxene, and amphibole minerals[13] which are often altered to serpentine by heat and fluids during and after eruption. Certain indicator minerals typically occur within diamantiferous kimberlites and are used as mineralogical tracers by prospectors, who follow the indicator trail back to the volcanic pipe which may contain diamonds. These minerals are rich in chromium (Cr) or titanium (Ti), elements which impart bright colors to the minerals. The most common indicator minerals are chromium garnets (usually bright red chromium-pyrope, and occasionally green ugrandite-series garnets), eclogitic garnets, orange titanium-pyrope, red high-chromium spinels, dark chromite, bright green chromium-diopside, glassy green olivine, black picroilmenite, and magnetite. Kimberlite deposits are known as blue ground for the deeper serpentinized part of the deposits, or as yellow ground for the near surface smectite clay and carbonate weathered and oxidized portion.[13]
Once diamonds have been transported to the surface by magma in a volcanic pipe, they may erode out and be distributed over a large area. A volcanic pipe containing diamonds is known as a primary source of diamonds. Secondary sources of diamonds include all areas where a significant number of diamonds have been eroded out of their kimberlite or lamproite matrix, and accumulated because of water or wind action. These include alluvial deposits and deposits along existing and ancient shorelines, where loose diamonds tend to accumulate because of their size and density. Diamonds have also rarely been found in deposits left behind by glaciers (notably in Wisconsin and Indiana); in contrast to alluvial deposits, glacial deposits are minor and are therefore not viable commercial sources of diamond.[13]

Material properties

Theoretically predicted phase diagram of carbon
Four panels. First, seven clear faceted gems, six small and a large one. Second, black material with uneven surface. Third, three parallel atomic sheets, each resembling a chicken wire hedge. Fourth, a boxed atomic structure containing tetrahedrally arranged balls connected by 0.15 nm bonds.
Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure.
A diamond is a transparent crystal of tetrahedrally bonded carbon atoms in a covalent network lattice (sp3) that crystallizes into the diamond lattice which is a variation of the face centered cubic structure. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness and thermal conductivity (900–2,320 W·m−1·K−1),[23] as well as wide bandgap and high optical dispersion.[24] Above 1,700 °C (1,973 K / 3,583 °F) in vacuum or oxygen-free atmosphere, diamond converts to graphite; in air, transformation starts at ~700 °C.[25] Diamond's ignition point is 720 – 800 °C in oxygen and 850 – 1,000 °C in air.[26] Naturally occurring diamonds have a density ranging from 3.15–3.53 g/cm3, with pure diamond close to 3.52 g/cm3.[1] The chemical bonds that hold the carbon atoms in diamonds together are weaker than those in graphite. In diamonds, the bonds form an inflexible three-dimensional lattice, whereas in graphite, the atoms are tightly bonded into sheets, which can slide easily over one another, making the overall structure weaker.[27]

Hardness

Diamond is the hardest known natural material on the Mohs scale of mineral hardness, where hardness is defined as resistance to scratching and is graded between 1 (softest) and 10 (hardest). Diamond has a hardness of 10 (hardest) on this scale.[28] Diamond's hardness has been known since antiquity, and is the source of its name.
Diamond hardness depends on its purity, crystalline perfection and orientation: hardness is higher for flawless, pure crystals oriented to the <111> direction (along the longest diagonal of the cubic diamond lattice).[29] Therefore, whereas it might be possible to scratch some diamonds with other materials, such as boron nitride, the hardest diamonds can only be scratched by other diamonds and nanocrystalline diamond aggregates.
The hardness of diamond contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in engagement or wedding rings, which are often worn every day.
The extreme hardness of diamond in certain orientations makes it useful in materials science, as in this pyramidal diamond embedded in the working surface of a Vickers hardness tester.
The hardest natural diamonds mostly originate from the Copeton and Bingara fields located in the New England area in New South Wales, Australia. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is associated with the crystal growth form, which is single-stage crystal growth. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice, all of which affect their hardness. It is possible to treat regular diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in hardness gauges.[20]
Somewhat related to hardness is another mechanical property toughness, which is a material's ability to resist breakage from forceful impact. The toughness of natural diamond has been measured as 7.5–10 MPa·m1/2.[30][31] This value is good compared to other gemstones, but poor compared to most engineering materials. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond has a cleavage plane and is therefore more fragile in some orientations than others. Diamond cutters use this attribute to cleave some stones, prior to faceting.[32] "Impact toughness" is one of the main indexes to measure the quality of synthetic industrial diamonds.[26]

Electrical conductivity

Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators.[33] The conductivity and blue color originate from boron impurity. Boron substitutes for carbon atoms in the diamond lattice, donating a hole into the valence band.[33]
Substantial conductivity is commonly observed in nominally undoped diamond grown by chemical vapor deposition. This conductivity is associated with hydrogen-related species adsorbed at the surface, and it can be removed by annealing or other surface treatments.[34][35]

Surface property

Diamonds are naturally lipophilic and hydrophobic, which means the diamonds' surface cannot be wet by water but can be easily wet and stuck by oil. This property can be utilized to extract diamonds using oil when making synthetic diamonds.[26] However, when diamond surfaces are chemically modified with certain ions, they are expected to become so hydrophilic that they can stabilize multiple layers of water ice at human body temperature.[36]

Chemical stability

Diamonds are not very reactive. Under room temperature diamonds do not react with any chemical reagents including strong acids and bases. A diamond's surface can only be oxidized a little by just a few oxidants[which?] at high temperature (below 1,000 °C). Therefore, acids and bases can be used to refine synthetic diamonds.[26]

Color

Main article: Diamond color
Diamond has a wide bandgap of 5.5 eV corresponding to the deep ultraviolet wavelength of 225 nanometers. This means pure diamond should transmit visible light and appear as a clear colorless crystal. Colors in diamond originate from lattice defects and impurities. The diamond crystal lattice is exceptionally strong and only atoms of nitrogen, boron and hydrogen can be introduced into diamond during the growth at significant concentrations (up to atomic percents). Transition metals Ni and Co, which are commonly used for growth of synthetic diamond by high-pressure high-temperature techniques, have been detected in diamond as individual atoms; the maximum concentration is 0.01% for Ni[37] and even less for Co. Virtually any element can be introduced to diamond by ion implantation.[38]
Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and brown color in diamonds. Boron is responsible for the blue color.[24] Color in diamond has two additional sources: irradiation (usually by alpha particles), that causes the color in green diamonds; and plastic deformation of the diamond crystal lattice. Plastic deformation is the cause of color in some brown[39] and perhaps pink and red diamonds.[40] In order of rarity, yellow diamond is followed by brown, colorless, then by blue, green, black, pink, orange, purple, and red.[32] "Black", or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice, known as a carbon flaw. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present.[32] The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as diamonds in the normal color range, and applies a grading scale from "D" (colorless) to "Z" (light yellow). Diamonds of a different color, such as blue, are called fancy colored diamonds, and fall under a different grading scale.[32]
In 2008, the Wittelsbach Diamond, a 35.56-carat (7.112 g) blue diamond once belonging to the King of Spain, fetched over US$24 million at a Christie's auction.[41] In May 2009, a 7.03-carat (1.406 g) blue diamond fetched the highest price per carat ever paid for a diamond when it was sold at auction for 10.5 million Swiss francs (6.97 million euro or US$9.5 million at the time).[42] That record was however beaten the same year: a 5-carat (1.0 g) vivid pink diamond was sold for $10.8 million in Hong Kong on December 1, 2009.[43]

Identification

Diamonds can be identified by their high thermal conductivity. Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds cut glass, but this does not positively identify a diamond because other materials, such as quartz, also lie above glass on the Mohs scale and can also cut it. Diamonds can scratch other diamonds, but this can result in damage to one or both stones. Hardness tests are infrequently used in practical gemology because of their potentially destructive nature.[28] The extreme hardness and high value of diamond means that gems are typically polished slowly using painstaking traditional techniques and greater attention to detail than is the case with most other gemstones;[10] these tend to result in extremely flat, highly polished facets with exceptionally sharp facet edges. Diamonds also possess an extremely high refractive index and fairly high dispersion. Taken together, these factors affect the overall appearance of a polished diamond and most diamantaires still rely upon skilled use of a loupe (magnifying glass) to identify diamonds 'by eye'.[44]

Industry

A clear faceted gem supported in four clamps attached to a wedding ring
A round brilliant cut diamond set in a ring
The diamond industry can be separated into two distinct categories: one dealing with gem-grade diamonds and another for industrial-grade diamonds. Both markets value diamonds differently.

Gem-grade diamonds

Main article: Diamond (gemstone)
A large trade in gem-grade diamonds exists. Unlike other commodities, such as most precious metals, there is a substantial mark-up in the retail sale of gem diamonds.[45] There is a well-established market for resale of polished diamonds (e.g. pawnbroking, auctions, second-hand jewelry stores, diamantaires, bourses, etc.). One hallmark of the trade in gem-quality diamonds is its remarkable concentration: wholesale trade and diamond cutting is limited to just a few locations; in 2003, 92% of the world's diamonds were cut and polished in Surat, India.[46] Other important centers of diamond cutting and trading are the Antwerp diamond district in Belgium, where the International Gemological Institute is based, London, the Diamond District in New York City, Tel Aviv, and Amsterdam. A single company – De Beers – controls a significant proportion of the trade in diamonds.[47] They are based in Johannesburg, South Africa and London, England. One contributory factor is the geological nature of diamond deposits: several large primary kimberlite-pipe mines each account for significant portions of market share (such as the Jwaneng mine in Botswana, which is a single large pit operated by De Beers that can produce between 12,500,000 carats (2,500 kg) to 15,000,000 carats (3,000 kg) of diamonds per year,[48]) whereas secondary alluvial diamond deposits tend to be fragmented amongst many different operators because they can be dispersed over many hundreds of square kilometers (e.g., alluvial deposits in Brazil).
The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers, the most important being Antwerp, where 80% of all rough diamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined are handled.[49] This makes Antwerp a de facto "world diamond capital".[50] Another important diamond center is New York City, where almost 80% of the world's diamonds are sold, including auction sales.[49] The DeBeers company, as the world's largest diamond miner holds a dominant position in the industry, and has done so since soon after its founding in 1888 by the British imperialist Cecil Rhodes. De Beers owns or controls a significant portion of the world's rough diamond production facilities (mines) and distribution channels for gem-quality diamonds. The Diamond Trading Company (DTC) is a subsidiary of De Beers and markets rough diamonds from De Beers-operated mines. De Beers and its subsidiaries own mines that produce some 40% of annual world diamond production. For most of the 20th century over 80% of the world's rough diamonds passed through De Beers,[51] but by 2001–2009 the figure had decreased to around 45%,[52] and by 2013 the company's market share had further decreased to around 38% in value terms and even less by volume.[53] De Beers sold off the vast majority of its diamond stockpile in the late 1990s – early 2000s[54] and the remainder largely represents working stock (diamonds that are being sorted before sale).[55] This was well documented in the press[56] but remains little known to the general public.
As a part of reducing its influence, De Beers withdrew from purchasing diamonds on the open market in 1999 and ceased, at the end of 2008, purchasing Russian diamonds mined by the largest Russian diamond company Alrosa.[57] As of January 2011, De Beers states that it only sells diamonds from the following four countries: Botswana, Namibia, South Africa and Canada.[58] Alrosa had to suspend their sales in October 2008 due to the global energy crisis,[59] but the company reported that it had resumed selling rough diamonds on the open market by October 2009.[60] Apart from Alrosa, other important diamond mining companies include BHP Billiton, which is the world's largest mining company;[61] Rio Tinto Group, the owner of Argyle (100%), Diavik (60%), and Murowa (78%) diamond mines;[62] and Petra Diamonds, the owner of several major diamond mines in Africa.
Diamond polisher in Amsterdam
Further down the supply chain, members of The World Federation of Diamond Bourses (WFDB) act as a medium for wholesale diamond exchange, trading both polished and rough diamonds. The WFDB consists of independent diamond bourses in major cutting centers such as Tel Aviv, Antwerp, Johannesburg and other cities across the USA, Europe and Asia.[32] In 2000, the WFDB and The International Diamond Manufacturers Association established the World Diamond Council to prevent the trading of diamonds used to fund war and inhumane acts. WFDB's additional activities include sponsoring the World Diamond Congress every two years, as well as the establishment of the International Diamond Council (IDC) to oversee diamond grading.
Once purchased by Sightholders (which is a trademark term referring to the companies that have a three-year supply contract with DTC), diamonds are cut and polished in preparation for sale as gemstones ('industrial' stones are regarded as a by-product of the gemstone market; they are used for abrasives).[63] The cutting and polishing of rough diamonds is a specialized skill that is concentrated in a limited number of locations worldwide.[63] Traditional diamond cutting centers are Antwerp, Amsterdam, Johannesburg, New York City, and Tel Aviv. Recently, diamond cutting centers have been established in China, India, Thailand, Namibia and Botswana.[63] Cutting centers with lower cost of labor, notably Surat in Gujarat, India, handle a larger number of smaller carat diamonds, while smaller quantities of larger or more valuable diamonds are more likely to be handled in Europe or North America. The recent expansion of this industry in India, employing low cost labor, has allowed smaller diamonds to be prepared as gems in greater quantities than was previously economically feasible.[49]
Diamonds which have been prepared as gemstones are sold on diamond exchanges called bourses. There are 28 registered diamond bourses in the world.[64] Bourses are the final tightly controlled step in the diamond supply chain; wholesalers and even retailers are able to buy relatively small lots of diamonds at the bourses, after which they are prepared for final sale to the consumer. Diamonds can be sold already set in jewelry, or sold unset ("loose"). According to the Rio Tinto Group, in 2002 the diamonds produced and released to the market were valued at US$9 billion as rough diamonds, US$14 billion after being cut and polished, US$28 billion in wholesale diamond jewelry, and US$57 billion in retail sales.[65]

Cutting

Main articles: Diamond cutting and Diamond cut
A large rectangular pink multifaceted gemstone, set in a decorative surround. The decoration includes a row of small clear faceted gemstones around the main gem's perimeter, and clusters of gems forming a crest on one side. The crest comprises a three-pointed crown faced by two unidentifiable animals.
The Darya-I-Nur Diamond—an example of unusual diamond cut and jewelry arrangement
Mined rough diamonds are converted into gems through a multi-step process called "cutting". Diamonds are extremely hard, but also brittle and can be split up by a single blow. Therefore, diamond cutting is traditionally considered as a delicate procedure requiring skills, scientific knowledge, tools and experience. Its final goal is to produce a faceted jewel where the specific angles between the facets would optimize the diamond luster, that is dispersion of white light, whereas the number and area of facets would determine the weight of the final product. The weight reduction upon cutting is significant and can be of the order of 50%.[66] Several possible shapes are considered, but the final decision is often determined not only by scientific, but also practical considerations. For example the diamond might be intended for display or for wear, in a ring or a necklace, singled or surrounded by other gems of certain color and shape.[67]
The most time-consuming part of the cutting is the preliminary analysis of the rough stone. It needs to address a large number of issues, bears much responsibility, and therefore can last years in case of unique diamonds. The following issues are considered:
  • The hardness of diamond and its ability to cleave strongly depend on the crystal orientation. Therefore, the crystallographic structure of the diamond to be cut is analyzed using X-ray diffraction to choose the optimal cutting directions.
  • Most diamonds contain visible non-diamond inclusions and crystal flaws. The cutter has to decide which flaws are to be removed by the cutting and which could be kept.
  • The diamond can be split by a single, well calculated blow of a hammer to a pointed tool, which is quick, but risky. Alternatively, it can be cut with a diamond saw, which is a more reliable but tedious procedure.[67][68]
After initial cutting, the diamond is shaped in numerous stages of polishing. Unlike cutting, which is a responsible but quick operation, polishing removes material by gradual erosion and is extremely time consuming. The associated technique is well developed; it is considered as a routine and can be performed by technicians.[69] After polishing, the diamond is reexamined for possible flaws, either remaining or induced by the process. Those flaws are concealed through various diamond enhancement techniques, such as repolishing, crack filling, or clever arrangement of the stone in the jewelry. Remaining non-diamond inclusions are removed through laser drilling and filling of the voids produced.[28]

Marketing

Marketing has significantly affected the image of diamond as a valuable commodity.
N. W. Ayer & Son, the advertising firm retained by De Beers in the mid-20th century, succeeded in reviving the American diamond market. And the firm created new markets in countries where no diamond tradition had existed before. N. W. Ayer's marketing included product placement, advertising focused on the diamond product itself rather than the De Beers brand, and associations with celebrities and royalty. Without advertising the De Beers brand, De Beers was also advertising its competitors' diamond products as well.[70] De Beers' market share dipped temporarily to 2nd place in the global market below Alrosa in the aftermath of the global economic crisis of 2008, down to less than 29% in terms of carats mined, rather than sold.[71] The campaign lasted for decades but was effectively discontinued by early 2011. De Beers still advertises diamonds, but the advertising now mostly promotes its own brands, or licensed product lines, rather than completely "generic" diamond products.[71] The campaign was perhaps best captured by the slogan "a diamond is forever".[7] This slogan is now being used by De Beers Diamond Jewelers,[72] a jewelry firm which is a 50%/50% joint venture between the De Beers mining company and LVMH, the luxury goods conglomerate.
Brown-colored diamonds constituted a significant part of the diamond production, and were predominantly used for industrial purposes. They were seen as worthless for jewelry (not even being assessed on the diamond color scale). After the development of Argyle diamond mine in Australia in 1986, and marketing, brown diamonds have become acceptable gems.[73][74] The change was mostly due to the numbers: the Argyle mine, with its 35,000,000 carats (7,000 kg) of diamonds per year, makes about one-third of global production of natural diamonds;[75] 80% of Argyle diamonds are brown.[76]

Industrial-grade diamonds

A diamond scalpel consisting of a yellow diamond blade attached to a pen-shaped holder
A scalpel with synthetic diamond blade
A polished metal blade embedded with small diamonds
Close-up photograph of an angle grinder blade with tiny diamonds shown embedded in the metal
A diamond knife blade used for cutting ultrathin sections (typically 70 to 350 nm for transmission electron microscopy.
Industrial diamonds are valued mostly for their hardness and thermal conductivity, making many of the gemological characteristics of diamonds, such as the 4 Cs, irrelevant for most applications. 80% of mined diamonds (equal to about 135,000,000 carats (27,000 kg) annually), are unsuitable for use as gemstones, and used industrially.[77] In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 570,000,000 carats (114,000 kg) of synthetic diamond is produced annually for industrial use. Approximately 90% of diamond grinding grit is currently of synthetic origin.[78]
The boundary between gem-quality diamonds and industrial diamonds is poorly defined and partly depends on market conditions (for example, if demand for polished diamonds is high, some lower-grade stones will be polished into low-quality or small gemstones rather than being sold for industrial use). Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which are known as bort.[79]
Industrial use of diamonds has historically been associated with their hardness, which makes diamond the ideal material for cutting and grinding tools. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial applications of this property include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive. Less expensive industrial-grade diamonds, known as bort, with more flaws and poorer color than gems, are used for such purposes.[80] Diamond is not suitable for machining ferrous alloys at high speeds, as carbon is soluble in iron at the high temperatures created by high-speed machining, leading to greatly increased wear on diamond tools compared to alternatives.[81]
Specialized applications include use in laboratories as containment for high pressure experiments (see diamond anvil cell), high-performance bearings, and limited use in specialized windows.[79] With the continuing advances being made in the production of synthetic diamonds, future applications are becoming feasible. The high thermal conductivity of diamond makes it suitable as a heat sink for integrated circuits in electronics.[82]

Mining

Approximately 130,000,000 carats (26,000 kg) of diamonds are mined annually, with a total value of nearly US$9 billion, and about 100,000 kg (220,000 lb) are synthesized annually.[83]
Roughly 49% of diamonds originate from Central and Southern Africa, although significant sources of the mineral have been discovered in Canada, India, Russia, Brazil, and Australia.[78] They are mined from kimberlite and lamproite volcanic pipes, which can bring diamond crystals, originating from deep within the Earth where high pressures and temperatures enable them to form, to the surface. The mining and distribution of natural diamonds are subjects of frequent controversy such as concerns over the sale of blood diamonds or conflict diamonds by African paramilitary groups.[84] The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world.
Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density. Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence, after which the final sorting steps are done by hand. Before the use of X-rays became commonplace,[66] the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.[32]
Siberia's Udachnaya diamond mine
Historically, diamonds were found only in alluvial deposits in Guntur and Krishna district of the Krishna River delta in Southern India.[85] India led the world in diamond production from the time of their discovery in approximately the 9th century BC[4][86] to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds were found in 1725.[4] Currently, one of the most prominent Indian mines is located at Panna.[87]
Diamond extraction from primary deposits (kimberlites and lamproites) started in the 1870s after the discovery of the Diamond Fields in South Africa.[88] Production has increased over time and now an accumulated total of 4,500,000,000 carats (900,000 kg) have been mined since that date.[89] Twenty percent of that amount has been mined in the last five years, and during the last 10 years, nine new mines have started production; four more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.[89]
In the U.S., diamonds have been found in Arkansas, Colorado, Wyoming, and Montana.[90][91] In 2004, the discovery of a microscopic diamond in the U.S. led to the January 2008 bulk-sampling of kimberlite pipes in a remote part of Montana.[91]
Today, most commercially viable diamond deposits are in Russia (mostly in Sakha Republic, for example Mir pipe and Udachnaya pipe), Botswana, Australia (Northern and Western Australia) and the Democratic Republic of Congo.[92] In 2005, Russia produced almost one-fifth of the global diamond output, reports the British Geological Survey. Australia boasts the richest diamantiferous pipe, with production from the Argyle diamond mine reaching peak levels of 42 metric tons per year in the 1990s.[90][93] There are also commercial deposits being actively mined in the Northwest Territories of Canada and Brazil.[78] Diamond prospectors continue to search the globe for diamond-bearing kimberlite and lamproite pipes.

Political issues

In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines, using proceeds from diamond sales to finance their operations. Diamonds sold through this process are known as conflict diamonds or blood diamonds.[84] Major diamond trading corporations continue to fund and fuel these conflicts by doing business with armed groups. In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central and western Africa, the United Nations, the diamond industry and diamond-trading nations introduced the Kimberley Process in 2002.[94] The Kimberley Process aims to ensure that conflict diamonds do not become intermixed with the diamonds not controlled by such rebel groups. This is done by requiring diamond-producing countries to provide proof that the money they make from selling the diamonds is not used to fund criminal or revolutionary activities. Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, some still find their way in. Conflict diamonds constitute 2–3% of all diamonds traded.[95] Two major flaws still hinder the effectiveness of the Kimberley Process: (1) the relative ease of smuggling diamonds across African borders, and (2) the violent nature of diamond mining in nations that are not in a technical state of war and whose diamonds are therefore considered "clean".[94]
The Canadian Government has set up a body known as Canadian Diamond Code of Conduct[96] to help authenticate Canadian diamonds. This is a stringent tracking system of diamonds and helps protect the "conflict free" label of Canadian diamonds.[97]

Synthetics, simulants, and enhancements

Synthetics

Main article: Synthetic diamond
Six crystals of cubo-octahedral shapes, each about 2 millimeters in diameter. Two are pale blue, one is pale yellow, one is green-blue, one is dark blue and one green-yellow.
Synthetic diamonds of various colors grown by the high-pressure high-temperature technique
Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth. The gemological and industrial uses of diamond have created a large demand for rough stones. This demand has been satisfied in large part by synthetic diamonds, which have been manufactured by various processes for more than half a century. However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size.[13] It is possible to make colorless synthetic gemstones that, on a molecular level, are identical to natural stones and so visually similar that only a gemologist with special equipment can tell the difference.[98]
The majority of commercially available synthetic diamonds are yellow and are produced by so-called High Pressure High Temperature (HPHT) processes.[99] The yellow color is caused by nitrogen impurities. Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis.[100]
A round, clear gemstone with many facets, the main face being hexagonal, surrounded by many smaller facets.
Colorless gem cut from diamond grown by chemical vapor deposition
Another popular method of growing synthetic diamond is chemical vapor deposition (CVD). The growth occurs under low pressure (below atmospheric pressure). It involves feeding a mixture of gases (typically 1 to 99 methane to hydrogen) into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves, hot filament, arc discharge, welding torch or laser.[101] This method is mostly used for coatings, but can also produce single crystals several millimeters in size (see picture).[83]
As of 2010, nearly all 5,000 million carats (1,000 tonnes) of synthetic diamonds produced per year are for industrial use. Around 50% of the 133 million carats of natural diamonds mined per year end up in industrial use.[98][102] The cost of mining a natural colorless diamond runs about $40 to $60 per carat, and the cost to produce a synthetic, gem-quality colorless diamond is about $2,500 per carat.[98] However, a purchaser is more likely to encounter a synthetic when looking for a fancy-colored diamond because nearly all synthetic diamonds are fancy-colored, while only 0.01% of natural diamonds are.[103]

Simulants

Main article: Diamond simulant
A round sparkling, clear gemstone with many facets.
Gem-cut synthetic silicon carbide set in a ring
A diamond simulant is a non-diamond material that is used to simulate the appearance of a diamond, and may be referred to as diamante. Cubic zirconia is the most common. The gemstone Moissanite (silicon carbide) can be treated as a diamond simulant, though more costly to produce than cubic zirconia. Both are produced synthetically.[104]

Enhancements

Main article: Diamond enhancement
Diamond enhancements are specific treatments performed on natural or synthetic diamonds (usually those already cut and polished into a gem), which are designed to better the gemological characteristics of the stone in one or more ways. These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.[105]
Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is diamond-like carbon—an amorphous carbonaceous material that has some physical properties similar to those of the diamond. Advertising suggests that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant. Techniques such as Raman spectroscopy should easily identify such a treatment.[106]

Identification

Early diamond identification tests included a scratch test relying on the superior hardness of diamond. This test is destructive, as a diamond can scratch diamond, and is rarely used nowadays. Instead, diamond identification relies on its superior thermal conductivity. Electronic thermal probes are widely used in the gemological centers to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. This test takes about 2–3 seconds.[107]
Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond, for example synthetic or natural, irradiated or non-irradiated, etc., requires more advanced, optical techniques. Those techniques are also used for some diamonds simulants, such as silicon carbide, which pass the thermal conductivity test. Optical techniques can distinguish between natural diamonds and synthetic diamonds. They can also identify the vast majority of treated natural diamonds.[108] "Perfect" crystals (at the atomic lattice level) have never been found, so both natural and synthetic diamonds always possess characteristic imperfections, arising from the circumstances of their crystal growth, that allow them to be distinguished from each other.[109]
Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin.[108] They also use specially made instruments to aid them in the identification process. Two screening instruments are the DiamondSure and the DiamondView, both produced by the DTC and marketed by the GIA.[110]
Several methods for identifying synthetic diamonds can be performed, depending on the method of production and the color of the diamond. CVD diamonds can usually be identified by an orange fluorescence. D-J colored diamonds can be screened through the Swiss Gemmological Institute's[111] Diamond Spotter. Stones in the D-Z color range can be examined through the DiamondSure UV/visible spectrometer, a tool developed by De Beers.[109] Similarly, natural diamonds usually have minor imperfections and flaws, such as inclusions of foreign material, that are not seen in synthetic diamonds.
Screening devices based on diamond type detection can be used to make a distinction between diamonds that are certainly natural and diamonds that are potentially synthetic. Those potentially synthetic diamonds require more investigation in a specialized lab. Examples of commercial screening devices are D-Screen (WTOCD / HRD Antwerp) and Alpha Diamond Analyzer (Bruker / HRD Antwerp).

Stolen diamonds

Occasionally large thefts of diamonds take place. In February 2013 armed robbers carried out a raid at Brussels Airport and escaped with gems estimated to be worth $50m (£32m; 37m euros). The gang broke through a perimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and large amounts of cash and diamonds recovered.[112]
The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is a mine or from an alluvial environment such as a beach or river - alluvial diamonds have smoother surfaces than those that have been mined. Determining the provenance of cut and polished stones is much more complex.
The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to fund violence. Before exporting, rough diamonds are certificated by the government of the country of origin. Some countries, such as Venezuela, are not party to the agreement. The Kimberley Process does not apply to local sales of rough diamonds within a country.
Diamonds may be etched by laser with marks invisible to the naked eye. Lazare Kaplan, a US-based company, developed this method. However, whatever is marked on a diamond can readily be removed.