cassiterite


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cassiterite

(kəsĭt`ərīt), heavy, brown-to-black mineral, tin oxide, SnO2, crystallizing in the tetragonal system. It is found as short prismatic crystals and as irregular masses, usually in veins and replacement deposits associated with granites. Since it is hard, heavy, and resistant to weathering, it often concentrates in alluvial deposits derived from cassiterite-bearing rocks. It is the principal ore of tin and is mined in many countries; the most important sources are Malaysia, Thailand, China, Indonesia, Bolivia, and Russia. Except for Bolivia, nearly all of this production is from alluvial deposits.

Cassiterite

 

(or tinstone), a mineral with the chemical composition Sno2. Theoretically it contains 78.62 percent Sn but usually includes impurities of Nb, Ta, Zr, Sc, W, and Fe; thus, the Sn content varies within 68–78 percent.

Cassiterite crystallizes in the tetragonal system, forming prismatic or dipyrimidal crystals. Geniculated twins are characteristic. The crystalline structure is analogous to that of rutile. Cassiterite is usually encountered in the form of small and large crystals, drusoid aggregates, or compact granular masses as well as in the form of cryptocrystalline, colloform segregations, concretions, and sinter formations. The color is dark brown, almost black, yellow with a reddish brown cast; nearly colorless varieties are also known. Cassiterite has an adamantine luster, a hardness of 6–7 on the mineralogical scale, and a density of 6, 040–7, 120 kg/m3 (lowest in light-colored cassiterite).

The deposits are usually genetically linked with granitic rocks. The most interesting commercial accumulations of the mineral are characteristic for hydrothermal quartz-cassiterite and sulfide-cassiterite veins. Cassiterite is stable in zones of oxidation and surface weathering; with the destruction of primary deposits, it accumulates in placers. In the USSR, cassiterite deposits are found in the northeast in Primor’e, in Middle Asia, and in the Kazakh SSR. Abroad, it is found in Malaysia, Thailand, Indonesia, the People’s Republic of China, Bolivia, Nigeria, and elsewhere. Cassiterite is the chief ore for obtaining tin.

A. B. PAVLOVSKII

cassiterite

[kə′sid·ə‚rīt]
(mineralogy)
SnO2 A yellow, black, or brown mineral that crystallizes in the tetragonal system in prisms terminated by dipyramids; the most important ore of tin. Also known as tin stone.
References in periodicals archive ?
Petrology carried out by CRAE determined that the tin is present as free fine cassiterite, usually 0.
Cassiterite (tin oxide) is the main ore source of tin, a highly
The provinces are rich in cassiterite and coltan, the minerals used to make phones, computers, games consoles and other electronics.
Violence and atrocities continue where armed groups profit from the sale of gold, coltan, wolframite and cassiterite mined by locals under inhumane conditions.
Especially since World War II, the pegmatites of the state of Minas Gerais have yielded some of the world's finest specimens of topaz, chrysoberyl, euclase, elbaite, and beryl (in all of its colored varieties); phosphate-rich pegmatites of the same state have furnished the world's finest specimens of brazilianite, beryllonite, eosphorite, hydroxylherderite, amblygonite and more; complex pegmatites of other kinds have provided cassiterite, xenotime, monazite and several rare-earth species; Brazilian specimens of titanite, phenakite, fluorapatite, kyanite, scheelite, spessartine and bertrandite are among the world's very best.
It was not immediately clear what the plane was carrying to Walikale, but the airstrip is often used to export cassiterite, a tin ore, out of Democratic Republic of Congo's bush.
The crystal structures in all cases were, however, the tetragonal cassiterite structure.
The recent inclusion of coltan and cassiterite in the DRC's EITI reporting is a step in the right direction.
Yet, besides these useful attributes lies the fact that the coltan trade based in eastern DRCongo is one of the various mineral trades--including gold, cassiterite, wolframite and diamonds--whose associated million-dollar illegal trafficking has served to brutally destabilise eastern Congo and fuel the ongoing conflict in which an estimated 5 million deaths have occurred since 1996.
Conflict flared in the Kivu provinces over mining access to coltan--short for columbite-tantalite and used in cell phones and computer chips--and cassiterite, a heavy dark mineral that is the chief source of tin.
Clinton addressed the question of the trade in minerals such as cassiterite and coltan, which are dug up in eastern Congo for use in consumer electronics such as mobile phones and whose sale funds armed groups in the region.