Cassiterite
Cassiterite with muscovite , from Xuebaoding, Huya, Pingwu, Mianyang, Sichuan, China (size: 100 x 95 mm, 1128 g)
General
Category	Oxide minerals
Formula (repeating unit)	SnO 2
IMA symbol	Cst [1]
Strunz classification	4.DB.05
Crystal system	Tetragonal
Crystal class	Ditetragonal dipyramidal (4/mmm) H-M symbol : (4/m 2/m 2/m)
Space group	P4 2 /mnm
Unit cell	a = 4.7382(4) A, c = 3.1871(1) A; Z = 2
Identification
Color	Black, brownish black, reddish brown, brown, red, yellow, gray, white; rarely colorless
Crystal habit	Pyramidic, prismatic, radially fibrous botryoidal crusts and concretionary masses; coarse to fine granular, massive
Twinning	Very common on {011}, as contact and penetration twins, geniculated; lamellar
Cleavage	{100} imperfect, {110} indistinct; partings on {111} or {011}
Fracture	Subconchoidal to uneven
Tenacity	Brittle
Mohs scale hardness	6?7
Luster	Adamantine to adamantine metallic, splendent; may be greasy on fractures
Streak	White to brownish
Diaphaneity	Transparent when light colored, dark material nearly opaque; commonly zoned
Specific gravity	6.98?7.1
Optical properties	Uniaxial (+)
Refractive index	n ω = 1.990?2.010 n ε = 2.093?2.100
Birefringence	δ = 0.103
Pleochroism	Pleochroic haloes have been observed. Dichroic in yellow, green, red, brown, usually weak, or absent, but strong at times
Fusibility	infusible
Solubility	insoluble
References	[2] [3] [4] [5] [6]

Cassiterite is a tin oxide mineral , SnO ₂ . It is generally opaque , but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains the most important source of tin today.

Occurrence [ edit ]

Most sources of cassiterite today are found in alluvial or placer deposits containing the weathering-resistant grains. The best sources of primary cassiterite are found in the tin mines of Bolivia , where it is found in crystallised hydrothermal veins. Rwanda has a nascent cassiterite mining industry. Fighting over cassiterite deposits (particularly in Walikale ) is a major cause of the conflict waged in eastern parts of the Democratic Republic of the Congo . ^{[7] [8]} This has led to cassiterite being considered a conflict mineral .

Cassiterite is a widespread minor constituent of igneous rocks . The Bolivian veins and the 4500 year old workings of Cornwall and Devon , England , are concentrated in high temperature quartz veins and pegmatites associated with granitic intrusives . The veins commonly contain tourmaline , topaz , fluorite , apatite , wolframite , molybdenite , and arsenopyrite . The mineral occurs extensively in Cornwall as surface deposits on Bodmin Moor , for example, where there are extensive traces of a hydraulic mining method known as streaming . The current major tin production comes from placer or alluvial deposits in Malaysia , Thailand , Indonesia , the Maakhir region of Somalia , and Russia . Hydraulic mining methods are used to concentrate mined ore, a process which relies on the high specific gravity of the SnO ₂ ore, of about 7.0.

Crystallography [ edit ]

Crystal twinning is common in cassiterite and most aggregate specimens show crystal twins. The typical twin is bent at a near-60-degree angle, forming an "elbow twin". Botryoidal or reniform cassiterite is called wood tin .

Cassiterite is also used as a gemstone and collector specimens when quality crystals are found.

Etymology [ edit ]

The name derives from the Greek kassiteros for "tin": this comes from the Phoenician word Cassiterid referring to the islands of Ireland and Great Britain , ^{[ citation needed ]} the ancient sources of tin; or, as Roman Ghirshman (1954) suggests, from the region of the Kassites , an ancient people in west and central Iran .

Use [ edit ]

It may be primary used as a raw material for tin extraction and smelting.

References [ edit ]

External links [ edit ]

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