Granada (mineralogia)

A Granada (do latim granatus, um grão) é o nome geral dos membros de um grupo de minerais com habitus cristalino constituído por dodecaedros e trapezoedros. São nesosilicatos de fórmula geral, A₃B₂(SiO₄)₃. As diversas variedades de granada podem incorporar diversos elementos químicos na sua estrutura, principalmente cálcio, magnésio, alumínio, ferro²⁺, ferro³⁺, cromo, manganês e titânio. As granadas não apresentam clivagem, mas mostram partição dodecaédrica. A fratura é concoidal a desigual; algumas variedades são muito resistentes e são valiosas para finalidades abrasivas. A dureza das granadas encontra-se no intervalo 6,5-7,5 e a densidade (peso específico) está entre 3,1 e 4,3. O brilho varia entre vítreo e resinoso, podendo ainda ser transparentes ou opacas, conforme a presença ou ausência de inclusões. As granadas podem apresentar as seguintes cores: vermelho, amarelo, marrom, preto, verde, ou incolor.
Os membros do grupo da granada subdividem-se através da sua variabilidade química.

Pingente em uvarovite, uma granada brilhante-verde rara. A dimensão é 2 cm (0,8 polegadas).

Um agregado de cristais de granada.

Amostra de rocha portadora de granada.

Índice 1 Membros do Grupo Granada 1.1 Piropo 1.2 Grossularite 1.3 Almandite 1.4 Espessartite 1.5 Uvarovite 1.6 Andradite 2 Granadas Artificiais 3 Referências

Membros do Grupo Granada

Piropo

Piropo, ou Rubi do Cabo, é uma granada de cor vermelho-sangue, devido a seu conteúdo de ferro e cromo. A sua fórmula é Mg₃Al₂(SiO₄)₃. O magnésio pode ser substituído em parte por cálcio e/ou ferro ferroso (Fe²⁺).
O piropo raramente possui inclusões, mas, quando presentes, estas se encontram em forma de cristais arredondados ou apresentam contorno irregular. Como todas as granadas, o piropo não possui clivagem, e a fratura é de subconcoide a irregular.
O piropo é encontrado em rocha vulcânica e depósitos aluviais e pode, juntamente com outros minerais, indicar a presença de rochas portadoras de diamantes. As localizações de jazidas incluem Arizona, África do Sul, Argentina, Austrália, Brasil, Myanmar, Escócia, Suíça e Tanzânia.
Os exemplares transparentes são usados como gemas. Uma variedade importante de piropo - a rodolite, do grego a rosa - é originária do condado de Macon na Carolina do Norte, é caracterizada pela cor violeta-vermelha e por constituir uma solução sólida de 2:1 entre piropo e almandina.
A palavra piropo deriva do grego pyropos, significando flamejante. Os piropos suíço e sul-africano são pedras de vermelho mais claro do que as pedras da Boémia, onde se utiliza o piropo na joalheria há mais de quinhentos anos.

Grossularite

Grossularite ou grossulária é uma granada de cálcio-alumínio com a fórmula Ca₃Al₂(SiO₄)₃, embora o cálcio pode em parte ser substituído por ferro ferroso (Fe²⁺) e o alumínio por ferro férrico (Fe³⁺). As cores mais comuns deste mineral são verde, canela, marrom, vermelho, e amarelo. A grossularite é um mineral típico de metamorfismo de contacto de calcários, onde se encontra associada a vesuvianite, diópsido, wollastonite e wernerite. Grossularite é um termo derivado da botânica.

Almandite

Almandite, almandina ou carbúnculo é uma granada do ferro-alumínio com a fórmula Fe₃Al₂(SiO₄)₃. As variedades transparentes podem ter bastante valor enquanto pedras preciosas. A almandite é um mineral comum em rochas metamórficas como o micaxisto, onde ocorre associado a estaurolite, distena, andaluzite, entre outros.

Espessartite

Espessartite ou Spessartita é uma granada de manganês e alumínio de fórmula Mn₃Al₂(SiO₄)₃. O nome é derivado da cidade de Spessart na Baviera. Esta variedade pode apresentar cores variadas, de acordo com o tipo e quantidade de impurezas. As mais famosas são as espessartites laranja de Madagascar e os exemplares violeta-vermelhos que ocorrem em riólitos do Colorado e Maine.

Uvarovite

Uvarovite ou Uvarovita é uma granada de cálcio e cromo de fórmula Ca₃Cr₂(SiO₄)₃. Dentro do grupo da granadas, é a variedade mais rara, surgindo em pequenos cristais de cor verde associados a cromita e serpentina.
A atraente e brilhante cor verde da uvarovite se deve à presença de cromo. Os cristais são muito frágeis, com fratura de subconcoide a irregular.
A uvarovite ocorre em rochas de serpentina. Os melhores cristais são encontrados nos Urais, na Rússia, em torno de cavidades ou fissuras na rocha. Outras fontes são a Finlândia, a Turquia e a Itália.

Andradite

Andradite ou Andradita é uma granada de cálcio e ferro de fórmula Ca₃Fe₂(SiO₄)₃, embora sejam comuns substituições catiónicas importantes. As cores dependem destas variações e podem ser vermelho, amarelo, marrom, verde ou preto. As variedades reconhecidas são topazolite (amarelo ou verde), demantoide (verde) e melantite (preto). A andradite pode ser encontrada em rochas ígneas de profundidade, como os sienitos, e em rochas metamórficas como os xistos e calcários. Seu nome homenageia o mineralogista brasileiro José Bonifácio de Andrada e Silva, mais conhecido por sua atuação na história política do Brasil, que lhe valeu o cognome de Patriarca da Independência.

Granadas Artificiais

• Granada de gadolínio e gálio (Gd₃Ga₂(GaO₄)₃) produzida para uso na indústria informática, conhecida comercialmente como GGG.
• Granada de ítrio e alumínio (Y₃Al₂(AlO₄)₃), gema artificial conhecida como YAG. Quando contém neodímio, é útil na focagem de lasers.

Referências

• Dana's Manual of Mineralogy ISBN 0-471-03288-3
• mindat.org
• Minerals.net
• USGS Garnet locations - USA

Categorias:

• Minerais
• Silicatos e germanatos
• Gemas

Cordierite

IOLITE

Cordierite
Cordierite from Italy
General
Category	Silicate mineral
Formula (repeating unit)	(Mg,Fe)2Al4Si5O18
Strunz classification	09.CJ.10
Dana classification	61.02.01.01 Cordierite group
Crystal symmetry	2/m 2/m 2/m Orthorhombic - Dipyramidal
Unit cell	a = 17.079 Å, b = 9.730 Å, c = 9.356 Å; Z = 4
Identification
Color	Blue, smoky blue, bluish violet; greenish, yellowish brown, gray; colorless to very pale blue in thin section
Crystal habit	Pseudo-hexagonal prismatic twins, as imbedded grains, and massive
Crystal system	Orthorhombic - Dipyramidal Space Group: C ccm
Twinning	Common on {110}, {130}, simple, lamellar, cyclical
Cleavage	Fair on {100}, poor on {001} and {010}
Fracture	Subconchoidal
Tenacity	Brittle
Mohs scale hardness	7 - 7.5
Luster	Greasy or vitreous
Streak	White
Specific gravity	2.57 - 2.66
Optical properties	Usually optically (-), sometimes (+); 2V = 0-90°
Refractive index	nα = 1.527 - 1.560 nβ = 1.532 - 1.574 nγ = 1.538 - 1.578 Indices increase with Fe content.
Pleochroism	X = pale yellow, green; Y = violet, blue-violet; Z = pale blue
Fusibility	on thin edges
Diagnostic features	Resembles quartz can be distinguished by pleochroism. Can be distinguished from corundum by its lower hardness
References	[1][2][3][4]

Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: (Mg,Fe)₂Al₃(Si₅AlO₁₈) to (Fe,Mg)₂Al₃(Si₅AlO₁₈).^[2] A high temperature polymorph exists, indialite, which is isostructural with beryl and has a random distribution of Al in the (Si,Al)₆O₁₈ rings.^[3]

Crystal structure of Cordierite

Contents 1 Name and discovery 2 Occurrence 3 Commercial use 4 Gem variety 5 See also 6 References 7 External links

Name and discovery

Cordierite, which was discovered in 1813, is named after the French geologist Louis Cordier (1777–1861).^[2]

Occurrence

Cordierite typically occurs in contact or regional metamorphism of argillaceous rocks. It is especially common in hornfels produced by contact metamorphism of pelitic rocks. Two common metamorphic mineral assemblages include sillimanite-cordierite-spinel and cordierite-spinel-plagioclase-orthopyroxene. Other associated minerals include garnet (cordierite-garnet-sillimanite gneisses) and anthophyllite.^[4][5] Cordierite also occurs in some granites, pegmatites, and norites in gabbroic magmas. Alteration products include mica, chlorite, and talc. Cordierite occurs in the granite contact zone at Geevor Tin Mine in Cornwall.

Commercial use

Catalytic converters are commonly made from ceramics containing a large proportion of synthetic cordierite. The manufacturing process deliberately aligns the cordierite crystals to make use of the very low thermal expansion seen for one axis. This prevents thermal shock cracking from taking place when the catalytic converter is used.^[6]

Gem variety

As the transparent variety iolite, it is often used as a gemstone. The name "iolite" comes from the Greek word for violet. Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It has also been called "water-sapphire" and "Vikings' Compass" because of its usefulness in determining the direction of the sun on overcast days, the Vikings having used it for this purpose.^[7] This works by determining the direction of polarization of the sky overhead. Light scattered by air molecules is polarized, and the direction of the polarization is at right angles to a line to the sun, even when the sun's disk itself is obscured by dense fog or lies just below the horizon.^[8]
Gem quality iolite varies in color from sapphire blue to blue violet to yellowish gray to light blue as the light angle changes. Iolite is sometimes used as an inexpensive substitute for sapphire. It is much softer than sapphires and is abundantly found in Australia (Northern Territory), Brazil, Burma, Canada (Yellowknife area of the Northwest Territories), India, Madagascar, Namibia, Sri Lanka, Tanzania and the United States (Connecticut). The largest iolite crystal found weighed more than 24,000 carats, and was discovered in Wyoming, US.^[9]

• 

  Left: rough specimen showing dichroism; right: cut stone
  
• 

  Facet cut Iolite gemstone
  
• 

  Pleochroism of Cordierite
  

See also

• List of minerals
• List of minerals named after people
• Sunstone (medieval)

References

1. ^ "Cordierite" (PDF). Handbook of Mineralogy. RRUFF™ Project.
2. ^ ^{a b c} "Cordierite". Mindat.org.
3. ^ ^{a b} http://webmineral.com/data/Cordierite.shtml Webmineral data
4. ^ ^{a b} Dana, James Dwight; Klein, Cornelis; Hurlbut, Cornelius S. (1985). Manual of Mineralogy (20th ed.). New York: John Wiley and Sons. pp. 395–396. ISBN 0-471-80580-7.
5. ^ Klein, Cornelis (2002). The Manual of Mineral Science (22nd ed.). John Wiley & Sons, Inc. ISBN 0-471-25177-1.
6. ^ Cybulski, Andrzej; Moulijn, Jacob A., eds. (2005). Structured Catalysts and Reactors (Second ed.). CRC Press. p. 35. ISBN 978-0-8247-2343-9.
7. ^ Guillot, Agnès; Meyer, Jean-Arcady (2010) [Published in French in 2008]. How To Catch a Robot Rat: When Biology Inspires Innovation [La bionique: Quand la science imite la Nature]. Translated by Susan Emanuel. The MIT Press. p. 212. ISBN 978-0-262-01452-6. "Many insects and a few birds perceive polarized light. The Vikings used cordierite for this purpose, a stone that allowed them to reckon the position of the sun by observing the stone's changes in color."
8. ^ Noel, Oscar; Bowling, Sue Ann (March 21, 1988). "Polar Navigation and the Sky Compass". Alaska Science Forum. Geophysical Institute, University of Alaska Fairbanks.
9. ^ Topix Local News: Casper, WY, Wyoming is Most Gemstone-Rich State in US, Sept. 13, 2011

Tanzanite

Tanzanite
Tanzanite rough stone and cut stone
General
Category	Sorosilicate
Formula (repeating unit)	(Ca2Al3(SiO4)(Si2O7)O(OH))
Strunz classification	09.BG.10
Identification
Color	Purple to blue
Crystal habit	Crystals flattened in an acicular manner, may be fibrously curved
Crystal system	Orthorhombic
Cleavage	Perfect {010} imperfect {100}
Fracture	Uneven to conchoidal
Mohs scale hardness	6.5
Luster	Vitreous, pearly on cleavage surfaces
Streak	White or colorless
Specific gravity	3.10–3.38
Optical properties	biaxial positive
Refractive index	1.69–1.70
Birefringence	0.006–0.018
Pleochroism	Present, dichroism or trichroism depending on color.

Tanzanite is the blue/purple variety of the mineral zoisite (a calcium aluminium hydroxy silicate) discovered in the Mererani Hills of Manyara Region in Northern Tanzania in 1967, near the city of Arusha and Mount Kilimanjaro. It is used as a gemstone. Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet and burgundy depending on crystal orientation.^[1] Tanzanite can also appear differently when viewed under alternate lighting conditions. The blues appear more evident when subjected to fluorescent light and the violet hues can be seen readily when viewed under incandescent illumination. Tanzanite in its rough state is usually a reddish brown color. It requires artificial heat treatment to 600 °C in a gemological oven to bring out the blue violet of the stone.^[2] Tanzanite is a rare gem.^[3][4] It is found only in the foothills of Mount Kilimanjaro. The mineral was named by Tiffany & Co. after Tanzania, the country in which it was discovered. Because it is relatively soft, tanzanite is most commonly set in necklaces and earrings.^[5]

Contents 1 Commercial history 1.1 World's largest tanzanite 1.1.1 Recent developments 2 Factors affecting value: grading 2.1 Heat treatment 3 Trivia 4 See also 5 References 6 External links

Commercial history

The craft work on tanzanite.

Emmanuel Merishiek Mollel, a Maasai tailor and part-time gold prospector living in Arusha (Tanzania), found transparent fragments of vivid blue and blue-purple gem crystals on a ridge near Mererani, some 40 km southeast of Arusha. He decided that the mineral was olivine (peridot) but quickly realized that it was not, so he took to calling it "dumortierite", a blue non-gem mineral. Shortly thereafter, D'Souza showed the stones to John Saul, a Nairobi-based consulting geologist and gemstone wholesaler who was then mining aquamarine in the region around Mount Kenya. Saul, with a Ph.D. from M.I.T., who later discovered the famous ruby deposits in the Tsavo area of Kenya, eliminated dumortierite and cordierite as possibilities, and sent samples to his father, Hyman Saul, vice president at Saks Fifth Avenue in New York. Hyman Saul brought the samples across the street to the Gemological Institute of America who correctly identified the new gem as a variety of the mineral zoisite. Correct identification was also made by mineralogists at Harvard University, the British Museum, and Heidelberg University, but the very first person to get the identification right was Ian McCloud, a Tanzanian government geologist based in Dodoma.^[6][7]
Officially called "blue zoisite" it was marketed as tanzanite by Tiffany & Co., who wanted to capitalize on the rarity of the gem, then only found in Tanzania, but who thought that "blue zoisite" (which might be pronounced like "blue suicide") wouldn't sell well.^[8] From 1967 to 1972, an estimated two million carats of tanzanite were mined in Tanzania before the mines were nationalized by the Tanzanian government.

World's largest tanzanite

The world's largest faceted tanzanite is 737.81 carats.^[9] One of the most famous large tanzanites (242 carats) is the "Queen of Kilimanjaro". It is set in a tiara and accented with 803 brilliant cut tsavorite garnets and 913 brilliant cut diamonds. The piece is part of the private collection of Michael Scott, the first CEO of Apple Computers.^[10]

Recent developments

In June 2003, the Tanzanian government introduced legislation banning the export of unprocessed tanzanite to India (like many gemstones, most tanzanite is cut in Jaipur). The ban has been rationalized as an attempt to spur development of local processing facilities, thereby boosting the economy and recouping profits. This ban was phased in over a two-year period, until which time only stones over 0.5 grams were affected.^{[citation needed]}
In April 2005, a company called TanzaniteOne Ltd. publicly announced that they had taken control of the portion of the tanzanite deposit known as "C-Block" (the main deposit is divided into five blocks). Prices for rough material on the open market have increased steadily as the company has solidified its control of the market. In August 2005, the largest-ever tanzanite crystal was found in the C-Block mine. The crystal weighs 16,839 carats (3.4 kg) and measures 8.7 in × 3.1 in × 2.8 in (22 cm × 8 cm × 7 cm).
The mining of tanzanite nets the Tanzanian government approximately US$20 million annually. The finished gems are sold mostly on the US market: sales total approximately US$500 million annually.^{[citation needed]}

A rough sample of tanzanite.

Factors affecting value: grading

There is no universally accepted method of grading colored gemstones. TanzaniteOne, a major commercial player in the tanzanite market, through its non-profit subsidiary, The Tanzanite Foundation,^[11] has introduced its own color-grading system.^[12] The new system's color-grading scales divide tanzanite colors into a range of hues, between blue violet and violet blue.
The normal primary and secondary hues in tanzanite are blue and purple, not violet. Purple is a modified spectral hue that lies halfway between red and blue. Tanzanite is a trichroic gemstone, meaning that light that enters the stone is divided into three sections, each containing a portion of the visible spectrum. After heating, tanzanite becomes dichroic. The dichroic colors are purple and blue. The hue range of tanzanite is blue-purple to purple-blue.^[13]
Clarity grading in colored gemstones is based on the eye-clean standard, that is, a gem is considered flawless if no inclusions are visible with the unaided eye (assuming 20/20 vision).^[14] The Gemological Institute of America classifies tanzanite as a Type I gemstone, meaning it is normally eye-flawless. Gems with eye-visible inclusions will be traded at deep discounts.

Heat treatment

Tanzanite is universally heat treated in a furnace, with a temperature between 550 and 700 degrees Celsius, to produce a range of hues between bluish-violet to violetish-blue. Some stones found close to the surface in the early days of the discovery were gem-quality blue without the need for heat treatment. The stones should not have any cracks or bubbles, as they could shatter or the cracks/ bubble could increase in size.
Since heat treatment is universal, it has no effect on price, and finished gems are assumed to be heat-treated. Tanzanite is sometimes found in other colors, such as green, although technically it would be called 'green zoisite' rather than tanzanite.^[15] Tanzanite may be subjected to other forms of treatment as well. Recently, coated Tanzanites were discovered and tested by the AGTA and AGL laboratories.^[16] A thin layer containing cobalt, determined by X-ray fluorescence, had been applied to improve the color. It was noted that "coatings in particular are not considered permanent", and in the United States are required to be disclosed at the point of sale.

Trivia

Tanzanite is the unofficial region gem of Manyara Region, where it was discovered and is still mined.

See also

• Manyara Region
• Arusha Region

References

1. ^ E. Skalwold. "Pleochroism: trichroism and dichroism in gems". Nordskip.com. Retrieved 2011-08-29.
2. ^ "YourGemologist / International School of Gemology Study of Heat Treatment". Yourgemologist.com. Retrieved 2011-08-29.
3. ^ http://web.archive.org/web/20090131195920/http://nationaljewelernetwork.com/njn/content_display/colored-stones/color-market-reports/e3i35bdd2d07c219452caefa3f76a183a6d?imw=Y
4. ^ http://bworldonline.com/Weekender020609/main.php?id=focus1^{[dead link]}
5. ^ "2005 Gem News Archive". Palagems.com. Retrieved 2011-08-29.
6. ^ "The Mineralogical Record - Merelani, Tanzania".
7. ^ "Tanzanite: Its discovery and early days - ICA's InColor Magazine. Summer 2007".
8. ^ "Tanzanite". Gemstone.org. Archived from the original on 2008-09-12. Retrieved 2011-08-29.
9. ^ http://www.palagems.com/Images/mineral_news/munich09_tanz.jpg
10. ^ "Royal Ontario Museum | Exhibitions & Galleries | Past Exhibitions | Light & Stone: Gems from the Collection of Michael Scott". Rom.on.ca. Retrieved 2011-08-29.
11. ^ The Tanzanite Foundation
12. ^ Tanzanite One Introduces Quality Grading, Pricing Changes and a Sight System JCK Online, 2005

Tanzanita

Tanzanite (Portugal)ou Tanzanita (Brasil) é uma variedade do mineral zoisite descoberta nos Montes Meralani no norte da Tanzânia em 1967 próximo de Arusha,afirma-se que por um natural de Goa de nome Manuel de Sousa. Desde então, a gema conheceu uma onda de popularidade, nomeadamente nos EUA, onde a Tiffany & Co. teve um papel fundamental tanto no seu baptismo, como na sua apresentação ao mercado e subsequente promoção.
Trata-se de uma gema popular e valiosa, sobretudo por sua cor e raridade. Digno de realce é o forte tricroísmo que apresenta (azul safira, violeta e verde dependendo da orientação do cristal). No entanto, a maior parte da tanzanite recebe tratamento térmico artificial para melhorar a sua cor, o que reduz significativamente esse tricroísmo.
Tem cor azul-safira, devida ao vanádio (tem 0,02%V). É transparente, tem dureza 6,5 a 7,5 na escala de Mohs, índice de refração 1,690 a 1,700 e birrefringência 0,010. A Tanzânia é ainda a única fonte conhecida e lá existem também zoisitas de outras cores que, aquecidas a 380 °C, ficam azul-safira, com reflexos roxos. (Pércio M. Branco, Dicionário de Mineralogia e Gemologia, 2008).

Rhodochrosite

Rhodochrosite
Rhodochrosite from Mina Capillitas, Province of Catamarca, Argentina
General
Category	Carbonate minerals
Formula (repeating unit)	MnCO3
Strunz classification	05.AB.05
Crystal symmetry	Trigonal hexagonal scalenohedral H-M symbol: (32/m) Space group: R3c
Unit cell	a = 4.777 Å, c = 15.67 Å; Z=6
Identification
Formula mass	114.95 g/mol
Color	Pink, rose-red, cherry-red, yellow, yellowish gray, cinnamon-brown, may be banded
Crystal habit	Rhombohedral and scalenohedral crystals; also commonly bladed, columnar, stalactitic, botryoidal, granular or massive
Crystal system	Trigonal
Twinning	On {1012} as contact and lamellar
Cleavage	On {1011} perfect; parting on {1012}
Fracture	Uneven, conchoidal
Tenacity	Brittle
Mohs scale hardness	3.5-4
Luster	Vitreous to pearly
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	3.7
Optical properties	Uniaxial (-)
Refractive index	nω = 1.814 - 1.816 nε = 1.596 - 1.598
Birefringence	δ = 0.218
Pleochroism	weak
Ultraviolet fluorescence	None
References	[1][2][3]

Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO₃. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. It streaks white, and its Mohs hardness varies between 3.5 and 4. Its specific gravity is between 3.5 and 3.7. It crystallizes in the trigonal system, and cleaves with rhombohedral carbonate cleavage in three directions. Crystal twinning often is present. It is transparent to translucent with refractive indices of nω=1.814 to 1.816, nε=1.596 to 1.598. It is often confused with the manganese silicate, rhodonite, but is distinctly softer.
Rhodochrosite forms a complete solid solution series with iron carbonate (siderite). Calcium, (as well as magnesium and zinc, to a limited extent) frequently substitutes for manganese in the structure, leading to lighter shades of red and pink, depending on the degree of substitution. It is for this reason that the most common color encountered is pink.

Contents 1 Occurrence and discovery 2 Use 2.1 Rhodochrosite and silver mining 3 Culture and legend 4 Gallery 5 See also 6 References

Occurrence and discovery

Rhodochrosite occurs as a hydrothermal vein mineral along with other manganese minerals in low temperature ore deposits as in the silver mines of Romania where it was first found. Banded rhodochrosite is mined in Capillitas, Argentina. Catamarca, Argentina has an old Incan silver mine that has produced fine stalactitic examples of rhodochrosite that are unique and very attractive. Cut cross-sections reveal concentric bands of light and dark rose colored layers. These specimens are carved and used for many ornamental purposes.^[4]
It was first described in 1813 in reference to a sample from Cavnic, Maramureş, present-day Romania. According to Dimitrescu and Radulescu, 1966 and to Papp, 1997, this mineral was described for the first time in Sacaramb, Romania, not in Cavnic, Romania. The name is derived from the Greek word ῥοδόχρως meaning rose-colored.

Use

Its main use is as an ore of manganese which is a key component of low-cost stainless steel formulations and certain aluminium alloys. Quality banded specimens are often used for decorative stones and jewelry. Due to its being relatively soft, and having perfect cleaveage, it is very difficult to cut, and therefore rarely found faceted in jewelry.

Rhodochrosite and silver mining

Manganese carbonate is extremely destructive to the amalgamation process used in the concentration of silver ores, and so until quality mineral specimens became highly sought after by collectors, they were often discarded on the mine dump.

Culture and legend

Colorado officially named rhodochrosite as its state mineral in 2002.^[5] Large specimens have been found in the Sweet Home Mine near Alma, Colorado.

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Small Rhodochrosite specimen featured in a mineral kit, from Wuton mine, Guangxi prov, China.

The Incas believed that rhodochrosite is the blood of their former rulers, turned to stone, therefore it is sometimes called "Rosa del Inca" or "Inca Rose".^[6]

Gallery

• 

  Large red rhodochrosite from Alma, Colorado
  
• 

  Pink is the most common color of Rhodochrosite. Specimen mined near Silverton, Colorado
  
• 

  The Alma King is the largest known rhodochrosite crystal; it was found in the Sweet Home Mine near Alma, Colorado. It is on display in the Denver Museum of Nature and Science.
  
• 

  Exhibit in La Plata Museum, La Plata, Argentina
  

See also

Manganoan Calcite

Wikimedia Commons has media related to: Rhodochrosite

References

1. ^ Handbook of Mineralogy
2. ^ Rhodochrosite data on Mindat
3. ^ Rhodochrosite data on Webmineral
4. ^ "Rhodochrosite (Manganese Carbonate)". Amethyst Galleries, Inc. Retrieved 2007-08-15.