By John Betterton
The metal indium, In, is a very rare element with an average crustal abundance of about 0.1 ppm. World production stands at around 600 tonnes per year with China, Canada, Japan and South Korea the main producers
The metal indium, In, is a very rare element
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with an average crustal abundance of about 0.1 ppm. World production stands at around 600 tonnes per year with China, Canada, Japan and South Korea the main producers.
In is mainly derived from zinc production and much is recycled. Despite its rarity it has numerous uses in the semi-conductor industries, such as in solar panels and flatscreen LCD’s, various semiconductors, LED’s Laser diodes, specialised solders, in alkaline batteries, various alloys including low melting alloys in fire-sprinkler systems, nuclear reactors, some types of medical imaging equipment, radiotracers, ball bearings in racing cars and as a light filter in sodium vapour lamps etc. The currently limited number of indium-bearing minerals is mostly concentrated within the sulphide class with a few others scattered in other classes. Most of the indium-bearings minerals known are described in this article.
Indium, In, occurs as small massive grains up to about 1 mm in size and crystallises in the tetragonal system. The mineral is grey colour with a yellowish tint. It is opaque with a metallic lustre and possesses a hardness of 3. Other physical properties are unknown and chemical analysis is best for certain identification. Indium is found in greisenized and albitized granite associated with silver. Several locations are known for this uncommon species and include the Orlovskoye Ta Deposit and the Sukhoi Log deposit, Lena Gold District, both in the Eastern-Siberian District, Russia; at the Perzhanskoe ore field, Zhytomyr Oblask, Ukraine; and in the Arashan Massif, Arashan Mts, Angren Region, Uzbekistan.
Indite, FeIn2S4, is found as massive grains and crystallises in the cubic system. It is iron-black in colour with a metallic lustre. The hardness is 5 and the calculated specific gravity is 4.5. Chemistry and x-rays are used for characterisation. It occurs in primary hydrothermal veins replacing cassiterite with dzhalindite. The mineral is known from only two locations in Russia. They are the Dzhalinda Sn Deposit, Khabarovskiy Kray, and the Verkhnee Tin Deposit, Primorskiy Kray, both in the Far-Eastern Region of the country.
Damiaoite, PtIn2, is white in colour with a metallic lustre. A polycrystalline globular habit and exsolved intergrowths is the noted form for this uncommon species. It has a black streak with a hardness of 5. The calculated specific gravity is very high at 10.9. Chemistry and limited distribution help is identification. This uncommon mineral is found with chalcopyrite, cooperite and yixunite etc in Pt veins in a garnet-amphibole pyroxinite. The sole occurrence is the PGE occurrence in Damiao village, Chengde County, Hebei Province, China.
Yixunite, Pt3In, rarely occurs as polycrystalline globules up to about 2 mm in size. It possesses a bright white colour with a metallic lustre. The mineral is opaque and the hardness is 6. Its calculated specific gravity is extremely high at 18.2. Chemistry, physical properties and x-rays are requited tests. It is found as an intergrowth with damiaoite in Pt veins in a garnet-amphibole pyroxinite. The single locality is the PGE occurrence in Damiao village, Chengde County, Hebei Province, China. Roquesite, CuInS2, occurs in high-temperature Sn-W-Bi-Mo hydrothermal veins in highly metamorphic rocks and as a later-stage mineral in skarns associated with chalcopyrite, wittichenite, chalcocite, covellite, bornite, sphalerite, tetrahedrite, lollingite, arsenopyrite and bismuth. It is found as tiny inclusions and is grey in polished section. Polysynthetic twinning is present and crystallises in the tetragonal system. This mineral has a metallic lustre and its hardness is 3.5 to 4. Other physical properties are not known. X-ray and chemical methods are required here. Specimens have been obtained from various widespread locations in France, England, Sweden, Czech Republic, Greece, Russia, Japan, South Korea, India, Canada, Argentina, Bolivia, and Brazil etc.
Sakuraiite, (Cu,Zn,Fe)3(In,Sn)S4, is a greenish steel-grey colour with a lead-grey streak and a olive tint. It possesses a metallic lustre and its hardness is 4. The calculated specific gravity is 4.4. Sakuraiite is cubic and forms exsolution textures in the mm size range. X-rays and chemical tests are needed to distinguish this species from others. The mineral occurs in banded hydrothermal vein deposits accompanied by stannite, sphalerite, chalcopyrite, cassiterite, matildite, arsenopyrite, quartz and calcite. This occasional sulphide is known from four separate sites. They are the Ikuno mine, Hygo Prefecture, Honshu Island and the Toyoha mine, Hokkaido, Japan; the San Roque deposit, Rio Negro and the Pirquitas Ag-Sn deposit, Rinconada Dept, Jujuy, Argentina.
Cadmoindite, CdIn2S4, is a cubic mineral that is found as nice octahedral crystals with an adamantine lustre. The colour is dark brown to black and is translucent in character with a brown streak. It is brittle and the specific gravity is calculated at 4.8. Chemistry, x-rays and mode of occurrence are helpful. Cadmoindite is found around high-temperature fumarole vents in association with pyrite, wurzite, rheniite and greenockite. Know locations for small specimens are the Kudriavy volcano, Iturup Isle, Kurily Islands, Far Eastern Region, Russia; and at the Katerina coal mine, Trutnov, Bohemia, Czech Republic.
Laforetite, AgInS4, is found as a tiny inclusions in galena with sphalerite, barite quartz, various carbonates, hocartite and pyrargyrite from a hydrothermal ore vein system. This mineral possesses polysynthetic twining and crystallises in the tetragonal system. It is brownish grey with abundant red inclusions in reflected light and is opaque. The hardness is around 3 and the calculated high specific gravity 4.9. Chemistry and x-rays are needed here. Samples have been acquired from the Montgros mine, La Boriette, Haute-Loire, France; and the Toyoha mine, Sapporo, Hokkaido, Japan.
Abramovite, Pb2SnInBiS7, is a silvery black mineral that is metallic and opaque with a black streak. It has a perfect cleavage. Other physical data is lacking. It occurs as lamellar crystals with striated slightly parallel to its elongation. Abramovite crystallises in the triclinic system. The mineral is best distinguished by x-ray and chemical methods along with its mode of occurrence. It is a product of precipitation from fumaroles associated with pyrrhotite, pyrite, wurzite, galena, halite, sylvite and anhydrite. This scarce species is known only from the Kupol fumarole field, Kudryavy volcano, Iturup Island, Southern Kurile Islands, Russia.
Dzhalindite, In(OH)3, occurs as a yellow-brown coloured mineral that is translucent. The habit is massive and crystallises in the cubic system. Few physical properties are known, but the specific gravity is 4.3. Dzhaldindite is probably a secondary mineral and found along fractures through various hydrothermal minerals in brecciated fesic volcanic rocks and in greisenized granite. Many minerals like indite, cassiterite, quartz, sphalerite, galena, chalcopyrite, roquesite, digenite, arsenopyrite and scorodite, accompany it. Chemistry and x-rays are used for certain identification. Samples come from various scattered locations in different countries such as Argentina, Brazil, China, Greece, Japan, Russia, USA and Uzbekistan.
Yanomamite, InAsO4·2H2O, forms small dipyramidal crystals belonging to the orthorhombic system up to about 0.2 mm in size. This rare but interesting species is pale green to yellow-green in colour with a vitreous lustre. It has a white streak and no cleavage.
The hardness is 3.5 to 4 and the calculated specific gravity is 3.8. Chemistry, occurrence and x-rays are useful hints. Yanomamite is a secondary mineral formed by replacing arsenopyrite in quartz-topaz greisen veins in granite with scorodite, sphalerite and cassiterite. The only currently known site for this mineral is the Mangebeira tin deposit, Passa e Fica, Goias, Brazil.
The minerals of carbon are to be described in the next article in this series.
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