quinta-feira, 31 de julho de 2014

Opala de Pedro II para o mundo

Opala de Pedro II para o mundo

Pedra brasileira alcança prestígio internacional e amplia os negócios de ourives em Pedro II, no Piauí.
A paisagem árida do interior do Piauí esconde a riqueza que a região oferece. Em Pedro II, no norte do estado, no entanto, ela está estampada já no portal da cidade, onde se lê que o lugar é a “terra da opala”.
Essa pedra preciosa, ainda pouco valorizada no país, movimenta a economia local e chega a render para os ourives até R$ 70 mil por mês. O município tem a única reserva de gemas nobres de opala no Brasil, que é a segunda maior do mundo – a primeira está na Austrália, que explorou minas brasileiras na década de 1970.
Pedra preciosa movimenta a economia local e chega a render para os ourives até R$ 70 mil por mês.
Afastada a desorganização e a mineração desenfreada, a cidade tomou as rédeas do negócio e foram criadas associações ligadas ao garimpo e à lapidação, estruturando o mercado da pedra.
O lapidário Juscelino Araújo Souza, pioneiro no segmento de joalherias, conta que quando começou, há quase 24 anos, o setor não estava organizado. “Tinha a pedra, mas não tinha quem fizesse o trabalho”, diz. A falta de mão de obra especializada o estimulou a abandonar as feiras livres, onde era ambulante, e procurar um curso de lapidação promovido pelo governo na época. Em 1992, Juscelino inaugurou a primeira empresa de lapidação de Pedro II e, em 2000, implantou ali uma área dedicada à joalheria.
Exportação e mercado interno
Cerca de 30% das opalas garimpadas são de alta qualidade e seguem para exportação.
Assim como a empresa de Juscelino, outras 30 se estabeleceram na região. Atualmente, elas são responsáveis pelo beneficiamento de 5 quilos de pedra bruta por mês, que resultam em 30 quilos de joias, já com valor agregado da prata ou do ouro utilizados na confecção das peças.
Opala do Piauí chega a render até R$ 500 mil anuais para lapidários do município.
Quanto maior o jogo de cores, mais valiosa é a pedra.
Cerca de 30% das opalas garimpadas são de alta qualidade e seguem para exportação, movimento que chega a render até R$ 500 mil anuais para lapidários do município. Os principais compradores são os Estados Unidos e a Alemanha, além de França e Suíça, que também valorizam o produto. Os 70% restantes ficam na região de Pedro II e são utilizados na produção de joias artesanais comercializadas no próprio Nordeste e em alguns estados brasileiros.
Segundo estimativas dos garimpeiros, ainda há jazidas inexploradas na região. Hoje existem cerca de 30 minas locais, e estudos sugerem que apenas 10% da reserva foi explorada. Com a organização do setor, as associações receberam o suporte que faltava para se desenvolverem. Em 2005, foi criado o Arranjo Produtivo da Opala, projeto que ajudou a reestruturar o mercado das pedras de Pedro II.
Opala lapidada e pronta para ser vendida.
Marcelo Morais, coordenador dos trabalhos, afirma que o negócio está mais orientado e hoje aspira até ao registro do selo de Indicação Geográfica, que já está em análise pelo Instituto Nacional da Propriedade Industrial (Inpi). A expectativa é de que até o fim do ano a indicação acompanhe o nome das opalas da cidade.
Juscelino, que também é o presidente da Associação para a Indicação Geográfica da Opala, diz que com a obtenção do selo a demanda deverá aumentar, o que pode elevar o preço final da joia em até 30%. Enquanto aguardam reconhecimento nacional, as associações se preparam para criar uma escola profissionalizante que começará a funcionar ainda em 2011. “O espaço irá atender o aumento da produção e oferecer formação para os jovens do município”, afirma.
Pedra Opala do Piauí
A vantagem de PEDRO II é que está 80% virgem, enquanto a AUSTRÁLIA está 99% explorada. PS= SÓ EXISTEM OPALA NOBRE EM 2 LUGARES NO MUNDO AUSTRÁLIA E BRASIL E O BRASIL ESTÁ PARA QUEM QUER GANHAR MUITO$$$$!!
Para os que querem enriquecer, aproveitem a oportunidade da pedra rara OPALA NOBRE em PEDROII, compram barato e revendem a 10x  no exterior ou em SP ou RIO, BH, NOS EUA 100X!!
IMPRESSIONANTE AS RESERVAS DE OPALA EM PEDROII INTOCADAS PELO HOMEM!!

Opal

Opal

Opal
Coober Pedy opal at the SAM 1.JPG
Precious opal replacing calcite of bivalve shells, from Coober Pedy; display specimen, South Australian Museum
General
Category Mineraloid
Formula
(repeating unit)
Hydrated silica. SiO2·nH2O
Identification
Color Colorless, white, yellow, red, orange, green, brown, black, blue
Crystal habit Irregular veins, in masses, in nodules
Crystal system Amorphous[1]
Cleavage None[1]
Fracture Conchoidal to uneven[1]
Mohs scale hardness 5.5–6[1]
Luster Subvitreous to waxy[1]
Streak White
Diaphaneity opaque, translucent, transparent
Specific gravity 2.15 (+.08, -.90)[1]
Density 2.09
Polish luster Vitreous to resinous[1]
Optical properties Single refractive, often anomalous double refractive due to strain[1]
Refractive index 1.450 (+.020, -.080) Mexican opal may read as low as 1.37, but typically reads 1.42–1.43[1]
Birefringence none[1]
Pleochroism None[1]
Ultraviolet fluorescence black or white body color: inert to white to moderate light blue, green, or yellow in long and short wave. May also phosphoresce; common opal: inert to strong green or yellowish green in long and short wave, may phosphoresce; fire opal: inert to moderate greenish brown in long and short wave, may phosphoresce.[1]
Absorption spectra green stones: 660nm, 470nm cutoff[1]
Diagnostic features darkening upon heating
Solubility hot saltwater, bases, methanol, humic acid, hydrofluoric acid
References [2][3]
Opal is a hydrated amorphous form of silica; its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Because of its amorphous character it is classed as a mineraloid, unlike the other crystalline forms of silica which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl and basalt. Opal is the national gemstone of Australia, which produces 97% of the world's supply.[4] This includes the production of the state of South Australia, which accounts for approximately 80% of the world's supply.[5]
The internal structure of precious opal makes it diffract light; depending on the conditions in which it formed, it can take on many colors. Precious opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare, whereas white and greens are the most common. It varies in optical density from opaque to semi-transparent.
Common opal, called "potch" by miners, does not show the display of color exhibited in precious opal.[6]

Precious opal

Precious opal consists of spheres of silicon dioxide molecules arranged in regular, closely packed planes. (Idealized diagram)
Multicolor Rough Crystal Opal from Coober Pedy, South Australia, expressing nearly every color of the visible spectrum.
Precious opal replacing Ichthyosaur backbone; display specimen, South Australian Museum
Brightness of the fire in Opal ranges on a scale of 1 to 5 (5 being the brightest)[7]
Australian Opal Doublet, a slice of precious opal with a backing of ironstone.
Precious opal shows a variable interplay of internal colors and even though it is a mineraloid, it has an internal structure. At micro scales precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic close-packed lattice. These ordered silica spheres produce the internal colors by causing the interference and diffraction of light passing through the microstructure of the opal.[8] It is the regularity of the sizes and the packing of these spheres that determines the quality of precious opal. Where the distance between the regularly packed planes of spheres is approximately half the wavelength of a component of visible light, the light of that wavelength may be subject to diffraction from the grating created by the stacked planes. The spacing between the planes and the orientation of planes with respect to the incident light determines the colors observed. The process can be described by Bragg's Law of diffraction.
Visible light of diffracted wavelengths cannot pass through large thicknesses of the opal. This is the basis of the optical band gap in a photonic crystal, of which opal is the best known natural example. In addition, microfractures may be filled with secondary silica and form thin lamellae inside the opal during solidification. The term opalescence is commonly and erroneously used to describe this unique and beautiful phenomenon, which is correctly termed play of color. Contrarily, opalescence is correctly applied to the milky, turbid appearance of common or potch opal. Potch does not show a play of color.
For gemstone use, most opal is cut and polished to form a cabochon. "Solid" opal refers to polished stones consisting wholly of precious opal. Opals too thin to produce a "solid," may be combined with other materials to form attractive gems. An opal doublet consists of a relatively thin layer of precious opal, backed by a layer of dark-colored material, most commonly ironstone, dark or black common opal (potch), onyx or obsidian. The darker backing emphasizes the play of color, and results in a more attractive display than a lighter potch. An opal triplet is similar to a doublet, but has a third layer, a domed cap of clear quartz or plastic on the top. The cap takes a high polish and acts as a protective layer for the opal. The top layer also acts as a magnifier, to emphasize the play of color of the opal beneath, which is often of lower quality. Triplet opals therefore have a more artificial appearance, and are not classed as precious opal.
Combined with modern techniques of polishing, doublet opal produces similar effect of black or boulder opals at a mere fraction of the price. Doublet opal also has the added benefit of having genuine opal as the top visible and touchable layer, unlike triplet opals.

Common opal

A piece of milky raw opal from Andamooka South Australia
A cabochon cut from a piece of opalized wood
An opal "triplet" from Andamooka South Australia showing blue and green fire
A rock showing striations of opal throughout
A close-up view of striations within opal
Besides the gemstone varieties that show a play of color, there are other kinds of common opal such as the milk opal, milky bluish to greenish (which can sometimes be of gemstone quality); resin opal, which is honey-yellow with a resinous luster; wood opal, which is caused by the replacement of the organic material in wood with opal;[9] menilite, which is brown or grey; hyalite, a colorless glass-clear opal sometimes called Muller's Glass; geyserite, also called siliceous sinter, deposited around hot springs or geysers; and diatomite or diatomaceous earth, the accumulations of diatom shells or tests.

Other varieties of opal

Fire opal from Mexico
Fire opal is a transparent to translucent opal, with warm body colors of yellow, orange, orange-yellow or red. It does not usually show any play of color, although occasionally a stone will exhibit bright green flashes. The most famous source of fire opals is the state of Querétaro in Mexico; these opals are commonly called Mexican fire opals. Fire opals that do not show play of color are sometimes referred to as jelly opals. Mexican opals are sometimes cut in their ryholitic host material if it is hard enough to allow cutting and polishing. This type of Mexican opal is referred to as a Cantera Opal. There is also a type of opal from Mexico referred to as Mexican Water Opal, which is a colorless opal which exhibits either a bluish or golden internal sheen.[10]
Girasol opal is a term sometimes mistakenly and improperly used to refer to fire opals as well as a type of transparent to semi-transparent type milky quartz from Madagascar which displays an asterism, or star effect, when cut properly. However, there is a true girasol opal[10] that is a type of halite opal, that exhibits a bluish glow or sheen that follows the light source around. It is not a play of color as seen in precious opal but rather an effect from microscopic inclusions. It is also sometimes referred to as water opal as well when it is from Mexico. The two most notable locations of this type of opal are Oregon and Mexico.[citation needed]
Peruvian opal (also called blue opal) is a semi-opaque to opaque blue-green stone found in Peru which is often cut to include the matrix in the more opaque stones. It does not display pleochroism. Blue opal also comes from Oregon in the Owhyee region as well as from Nevada around Virgin Valley.[citation needed]

Sources of opal

Gem Opal from Brazil
Polished opal from Yowah (Yowah Nut[11]), Queensland, Australia
Multi-Colored solid black opal cabochon from Lightning Ridge, NSW
Australia produces around 97% of the world's opal. 90% is called 'light opal' or white and crystal opal. White makes up 60% of the opal productions but cannot be found in all of the opal fields. Crystal opal or pure hydrated silica makes up 30% of the opal produced, 8% is black and only 2% is boulder opal.[citation needed]
The town of Coober Pedy in South Australia is a major source of opal. The world's largest and most valuable gem opal "Olympic Australis" was found in August 1956 at the "Eight Mile" opal field in Coober Pedy. It weighs 17,000 carats (3450 grams) and is 11 inches (280 mm) long, with a height of 4 34 inches (120 mm) and a width of 4 12 inches (110 mm).[citation needed]
Boulder Opal, Carisbrooke Station near Winton, Queensland
The Mintabie Opal Field located approximately 250 km north west of Coober Pedy has also produced large quantities of crystal opal and also the rarer black opal. Over the years it has been sold overseas incorrectly as Coober Pedy Opal. The black opal is said to be some of the best examples found in Australia.
Andamooka in South Australia is also a major producer of matrix opal, crystal opal, and black opal. Another Australian town, Lightning Ridge in New South Wales, is the main source of black opal, opal containing a predominantly dark background (dark-gray to blue-black displaying the play of color). Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix. It is found sporadically in western Queensland, from Kynuna in the north, to Yowah and Koroit in the south.[12] Its largest quantities are found around Jundah and Quilpie (known as the "home of the Boulder Opal"[13]) in South West Queensland. Australia also has opalised fossil remains, including dinosaur bones in New South Wales, and marine creatures in South Australia.[14] The rarest type of Australian opal is "pipe" opal, closely related to boulder opal, which forms in sandstone with some iron-oxide content, usually as fossilized tree roots.[citation needed]
Multi-colored rough opal specimen from Virgin Valley, Nevada, US
The Virgin Valley[15] opal fields of Humboldt County in northern Nevada produce a wide variety of precious black, crystal, white, fire, and lemon opal. The black fire opal is the official gemstone of Nevada. Most of the precious opal is partial wood replacement. The precious opal is hosted and found within a subsurface horizon or zone of bentonite in-place which is considered a "lode" deposit. Opals which have weathered out of the in-place deposits are alluvial and considered placer deposits. Miocene age opalised teeth, bones, fish, and a snake head have been found. Some of the opal has high water content and may desiccate and crack when dried. The largest producing mines of Virgin Valley have been the famous Rainbow Ridge,[16] Royal Peacock,[17] Bonanza,[18] Opal Queen,[19] and WRT Stonetree/Black Beauty[20] Mines. The largest unpolished Black Opal in the Smithsonian Institution, known as the "Roebling Opal,"[21] came out of the tunneled portion of the Rainbow Ridge Mine in 1917, and weighs 2,585 carats. The largest polished black opal in the Smithsonian Institution comes from the Royal Peacock opal mine in the Virgin Valley, weighing 160 carats, known as the "Black Peacock."[22]
Another source of white base opal or creamy opal in the United States is Spencer, Idaho.[citation needed] A high percentage of the opal found there occurs in thin layers.
Other significant deposits of precious opal around the world can be found in the Czech Republic, Slovakia, Hungary, Turkey, Indonesia, Brazil (in Pedro II, Piauí[23]), Honduras, Guatemala, Nicaragua and Ethiopia.
In late 2008, NASA announced that it had discovered opal deposits on Mars.[24]

Synthetic opal

As well as occurring naturally, opals of all varieties have been synthesized experimentally and commercially. The discovery of the ordered sphere structure of precious opal led to its synthesis by Pierre Gilson in 1974.[8] The resulting material is distinguishable from natural opal by its regularity; under magnification, the patches of color are seen to be arranged in a "lizard skin" or "chicken wire" pattern. Furthermore, synthetic opals do not fluoresce under UV light. Synthetics are also generally lower in density and are often highly porous.
Two notable producers of synthetic opal are the companies Kyocera and Inamori of Japan. Most so-called synthetics, however, are more correctly termed "imitation opal", as they contain substances not found in natural opal (e.g., plastic stabilizers). The imitation opals seen in vintage jewelry are often foiled glass, glass-based "Slocum stone", or later plastic materials.
Other research in macroporous structures have yielded highly ordered materials that have similar optical properties to opals and have been used in cosmetics.[25]

Local atomic structure of opals

The lattice of spheres of opal that cause the interference with light are several hundred times larger than the fundamental structure of crystalline silica. As a mineraloid, there is no unit cell that describes the structure of opal. Nevertheless, opals can be roughly divided into those that show no signs of crystalline order (amorphous opal) and those that show signs of the beginning of crystalline order, commonly termed cryptocrystalline or microcrystalline opal.[26] Dehydration experiments and infrared spectroscopy have shown that most of the H2O in the formula of SiO2·nH2O of opals is present in the familiar form of clusters of molecular water. Isolated water molecules, and silanols, structures such as Si-O-H, generally form a lesser proportion of the total and can reside near the surface or in defects inside the opal.
The structure of low-pressure polymorphs of anhydrous silica consist of frameworks of fully corner bonded tetrahedra of SiO4. The higher temperature polymorphs of silica cristobalite and tridymite are frequently the first to crystallize from amorphous anhydrous silica, and the local structures of microcrystalline opals also appear to be closer to that of cristobalite and tridymite than to quartz. The structures of tridymite and cristobalite are closely related and can be described as hexagonal and cubic close-packed layers. It is therefore possible to have intermediate structures in which the layers are not regularly stacked.
The crystal structure of crystalline α-cristobalite. Locally, the structures of some opals, opal-C, are similar to this.

Microcrystalline opal

Lussatite (Opale-Ct)
Opal-CT has been interpreted as consisting of clusters of stacking of cristobalite and tridymite over very short length scales. The spheres of opal in opal-CT are themselves made up of tiny microcrystalline blades of cristobalite and tridymite. Opal-CT has occasionally been further subdivided in the literature. Water content may be as high as 10 wt%. Lussatite is a synonym. Opal-C, also called Lussatine, is interpreted as consisting of localized order of \alpha-cristobalite with a lot of stacking disorder. Typical water content is about 1.5wt%.

Non-crystalline opal

Two broad categories of non-crystalline opals, sometimes just referred to as "opal-A", have been proposed. The first of these is opal-AG consisting of aggregated spheres of silica, with water filling the space in between. Precious opal and potch opal are generally varieties of this, the difference being in the regularity of the sizes of the spheres and their packing. The second "opal-A" is opal-AN or water-containing amorphous silica-glass. Hyalite is another name for this.
Non-crystalline silica in siliceous sediments is reported to gradually transform to opal-CT and then opal-C as a result of diagenesis, due to the increasing overburden pressure in sedimentary rocks, as some of the stacking disorder is removed.[27]

Naming

The word opal is adapted from the Roman term opalus, but the origin of this word is a matter of debate. However, most modern references suggest it is adapted from the Sanskrit word úpala.[28]
References to the gem are made by Pliny the Elder. It is suggested it was adapted it from Ops, the wife of Saturn and goddess of fertility. The portion of Saturnalia devoted to Ops was "Opalia", similar to opalus.
Another common claim that the term is adapted from the Greek word, opallios. This word has two meanings, one is related to "seeing" and forms the basis of the English words like "opaque", the other is "other" as in "alias" and "alter". It is claimed that opalus combined these uses, meaning "to see a change in color". However, historians have noted that the first appearances of opallios do not occur until after the Romans had taken over the Greek states in 180 BC, and they had previously used the term paederos.[28]
However, the argument for the Sanskrit origin is strong. The term first appears in Roman references around 250 BC, at a time when the opal was valued above all other gems. The opals were supplied by traders from the Bosporus, who claimed the gems were being supplied from India. Before this the stone was referred to by a variety of names, but these fell from use after 250 BC.

Historical superstitions

In the Middle Ages, opal was considered a stone that could provide great luck because it was believed to possess all the virtues of each gemstone whose color was represented in the color spectrum of the opal.[29] It was also said to confer the power of invisibility if wrapped in a fresh bay leaf and held in the hand.[29][30] Following the publication of Sir Walter Scott's Anne of Geierstein in 1829, however, opal acquired a less auspicious reputation. In Scott's novel, the Baroness of Arnheim wears an opal talisman with supernatural powers. When a drop of holy water falls on the talisman, the opal turns into a colorless stone and the Baroness dies soon thereafter. Due to the popularity of Scott's novel, people began to associate opals with bad luck and death.[29] Within a year of the publishing of Scott's novel in April 1829, the sale of opals in Europe dropped by 50%, and remained low for the next twenty years or so.[31]
Even as recently as the beginning of the 20th century, it was believed that when a Russian saw an opal among other goods offered for sale, he or she should not buy anything more since the opal was believed to embody the evil eye.[29]
Opal is considered the birthstone for people born in October or under the sign of Scorpio and Libra.

Famous opals

Opala nobre

Opala nobre



Opala
Um bracelete com opala. O tamanho da pedra é 18 por 15 milímetros (0.7 por 0.6 polegadas)
Categoria Mineralóide
Cor branco, preto, vermelho, laranja, a maior parte do espectro completo, incolor, iridiscente
Fórmula química Hidrato sílica. SiO2·nH2O
Recursos de diagnóstico escurecimento após aquecimento
Propriedades cristalográficas
Sistema cristalino Amorfo1
Hábito cristalino Irregular veias, nas massas, nos nódulos
Propriedades óticas
Índice refrativo 1.450 (+.020, -.080) Opala mexicana pode ler um valor tão baixo quanto 1,37, mas normalmente lê 1.42–1.431
Birrefringência none1
Propriedades ópticas Refração simples, muitas vezes anômalo de dupla refração devido à tensão1
Fluorescência ultravioleta pode ser fortemente fluorescente à luz UV, geralmente em amarelo e azul ou, na opala comum, em verde-maçã ou verde-amarelado.
Espectro de absorção pedras verdes: 660nm, 470nm cutoff1
Propriedades físicas
Polimento Vítreo a resinoso1
Dureza 5.5–6.51
Solubilidade quente água salgada, bases, metanol, ácido húmico, ácido fluorídrico
Clivagem Não1
Fratura Conchoidal para desigual1
Brilho Subvítreo para ceroso1
Risca Branco
Referências 2 3
opala de fogo
O mineralóide Opala é sílica amorfa hidratada, o percentual de água pode chegar a 20%. Por ser amorfo, ele não tem formato de cristal, ocorrendo em veios irregulares, massas, e nódulos. Tem a fratura conchoidal, brilho vítreo, dureza na escala de Mohs de 5,5-6,6, gravidade específica 2,1-2,3, e uma cor altamente variável.

Características

A opala pode ser branca, incolor, azul-leitosa, cinza, vermelha, amarela, verde, marrom e preta. Frequentemente muitas dessas cores podem ser vistas simultaneamente, em decorrência de interferência e difração da luz que passa por aberturas regularmente arranjadas dentro do microestructura do opala, fenômeno conhecido como jogo de cores ou difração de Bragg. A estrutura da opala é formada por esferas de cristobalita ou de sílica amorfa, regularmente dispostas, entre as quais há água, ar ou geis de sílica. Quando as esferas têm o mesmo tamanho e um diâmetro semelhante ao comprimento de onda das radiações da luz visível, ocorre difração da luz e surge o jogo de cores da opala nobre. Se as esferas variam de tamanho, não há difração e tem-se a opala comum.
O termo opalescência é usado geral e erroneamente para descrever este fenômeno original e bonito, que é o jogo da cores. Na verdade, opalescência é o que mostra opala leitosa, de aparência turva ou opala do potch, sem jogo de cores.
As veias de opala que mostram jogo de cores são frequentemente muito finas, e isso leva à necessidade de lapidar a pedra de modos incomuns. Um doublet de opala é uma camada fina de opala colorida sobre um material escuro como basalto ou obsidiana. A base mais escura ressalta o jogo de cores, resultando numa aparência mais atraente do que um potch mais claro. O triplet de opala é obtido com uma base escura e com um revestimento protetor de quartzo incolor (cristal de rocha), útil por ser a opala relativamente delicada.
Dada a textura das opalas, pode ser difícil obter um brilho razoável.
As variedades de opala que mostram jogo de cores, as opalas preciosas, recebem diversos nomes; do mesmo modo, há vários tipos de opala comum, tais como: opala leitosa (um azulado leitoso a esverdeado); opala resina (amarelo-mel com um bilho resinoso); opala madeira (formada pela substituição da madeira com opala); Menilite (marrom ou cinza) e hialite, uma rara opala incolor chamada às vezes Vidro de Müller.
A opala é um gel que é depositado em temperatura relativamente baixa em fissuras de quase todo tipo de rocha, geralmente sendo encontrado nas formações ferro-manganesíferas, arenito, e basalto. Pode se formar também em outros tipos de materiais, como nós de bambus. A palavra opala vem do sânscrito upala, do grego opallos e do latim opalus, significando "pedra preciosa."
A opala é um dos minerais que podem formar fósseis, por substituição. Os fósseis resultantes, embora possam não ser especialmente valiosos do ponto de vista científico, atraem colecionadores por sua beleza.
A maior parte da opala produzida no mundo (98%) vem da Austrália. A cidade de Coober Pedy, em particular, é uma das principais fontes. As variedades terra comum, água, geléia, e opala de fogo são encontradas na maior parte no México e Mesoamérica.
Existem opalas sintéticas, que estão disponíveis experimental e comercialmente. O material resultante é distinguível da opala natural por sua regularidade; sob ampliação, as áreas com diferentes cores são arranjadas em forma de "pele de lagarto" ou padrão "chicken wire". As opalas sintéticas são distinguidas das naturais mais pela falta de fluorescência sob luz UV. São também geralmente de densidade mais baixa e frequentemente mais porosas.
Dois notáveis produtores do opala sintética são as companhias Kyocera e Inamori do Japão. A maioria das opalas chamadas sintéticas, entretanto, são denominadas mais corretamente de imitações, porque contêm substâncias não encontradas na opala natural (por exemplo, estabilizadores plásticos). As opalas Gilson vistas frequentemente em jóias vintage são, na realidade, um vidro laminado.

Reservas no Brasil

Pedro II - Piauí

A opala também é encontrada no Brasil, municipío de Pedro II (Piauí), localizado ao Norte do Estado.
A opala de Pedro II (Piauí) é a única de qualidade nobre no Brasil e suas reservas, juntamente com as reservas australianas, formam as únicas jazidas de opala de importância no planeta. As reservas de Pedro II são: 12.469,354 kg de reservas medidas; 50.269,416 kg de reservas indicadas e 38.529,230 kg de reservas inferidas.
A opala, pedra preciosa conhecida por produzir lampejos das sete cores do arco-íris, tem sua maior jazida brasileira no município piauiense de Pedro II.
A opala é a Gema oficial da Austrália.

Kinross tem queda de 72% nos ganhos do segundo trimestre

Kinross tem queda de 72% nos ganhos do segundo trimestre
A produção da mineradora atingiu 680.000 onças de ouro que foram negociadas a um preço médio de US$742/oz. O AISC (all-in sustaining costs ) foi de US$976/oz uma queda de 6%.

Os ganhos líquidos do T2 foram de US$32,9 milhões uma queda de 72,4% em relação ao mesmo período de 2013. A Kinross volta aos lucros o que não ocorreu em 2013 quando teve um prejuízo líquido de $2,5 bilhões .

Vale: lucro melhor que 2013, mas abaixo das expectativas

Vale: lucro melhor que 2013, mas abaixo das expectativas
O lucro da Vale no segundo trimestre, foi de US$1,43 bilhões, melhor do que o lucro no mesmo período de 2013. A mineradora teve um desempenho afetado pelos ajustes de desvalorização de ativos. O Projeto Simandou pesou e a Vale teve que declarar um prejuízo de US$774 milhões.

No período a empresa exportou 76,9 milhões de toneladas de minério de ferro e pelotas, um crescimento de 6,6%. O preço médio do minério vendido foi de US$84,60 por tonelada demonstrando que nem tudo é minério de alta qualidade...

O EBITDA da Vale caiu 16% no período para US$4,1 bilhões. Mesmo assim o número foi acima do que os analistas esperavam.

Outro ponto que chamou a atenção foi a queda dos investimentos em 28,3% mostrando uma nova estratégia que visa focar no seu core business. 

Yamana: melhor do que as expectativas

Yamana: melhor do que as expectativas
O balancete trimestral publicado pela Yamana mostrou surpresas positivas. A mineradora conseguiu se superar, aumentando a produção em 20% e reduzindo os seus custos.

Esse desempenho foi a causa de um crescimento extraordinário de 84% no cash flow do segundo trimestre. A produção no trimestre atingiu 331.765 onças de ouro. O AISC (all-in sustainig costs) por onça equivalente foi de US$915, 6% menor do que o do primeiro trimestre.

A Yamana mostrou ser uma das grandes empresas de mineração fazendo tudo certo e calando a boca dos bancos, como o HSBC, que prematuramente depreciou as suas ações.