كاسيتريت

(تم التحويل من أكسيد القصدير)
Cassiterite
4447M-cassiterite.jpg
Cassiterite with muscovite, from Xuebaoding, Huya, Pingwu, Mianyang, Sichuan, China (size: 100 x 95 mm, 1128 g)
العامة
التصنيفOxide minerals
الصيغة
(repeating unit)
SnO2
تصنيف سترونز4.DB.05
النظام البلوريTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupP42/mnm
Unit cella = 4.7382(4) Å,
c = 3.1871(1) Å; Z = 2
التعرف
ColorBlack, brownish black, reddish brown, brown, red, yellow, gray, white; rarely colorless
Crystal habitPyramidic, prismatic, radially fibrous botryoidal crusts and concretionary masses; coarse to fine granular, massive
TwinningVery common on {011}, as contact and penetration twins, geniculated; lamellar
Cleavage{100} imperfect, {110} indistinct; partings on {111} or {011}
FractureSubconchoidal to uneven
TenacityBrittle
Mohs scale hardness6–7
LusterAdamantine to adamantine metallic, splendent; may be greasy on fractures
StreakWhite to brownish
DiaphaneityTransparent when light colored, dark material nearly opaque; commonly zoned
الجاذبية النوعية6.98–7.1
الصفات البصريةUniaxial (+)
Refractive indexnω = 1.990–2.010 nε = 2.093–2.100
Birefringenceδ = 0.103
PleochroismPleochroic haloes have been observed. Dichroic in yellow, green, red, brown, usually weak, or absent, but strong at times
قابلية الانصهارinfusible
قابلية الذوبانinsoluble
References[1][2][3][4][5]

أكسيد القصدير Cassiterite أهم خامات القصدير المعدنية، ويسمى أحيانًا باسم حجر القصدير الرمز الكيميائي (SnO2). ولأكسيد القصدير لمعان فلزي خفيف وله لون بني أو أسود، ويوجد عادة مع الكوارتز في عروق صخور الجرانيت أو بالقرب منها. وتنتج ماليزيا حوالي ربع الإنتاج العالمي من أكسيد القصدير، بينما تعد بوليفيا وإندونيسيا والبرازيل والصين مصادر مهمة أيضًا لهذا المعدن.

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التواجد

Most sources of cassiterite today are found in alluvial or placer deposits containing the resistant weathered 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.[6][7] 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 SnO2 ore, of about 7.0.


علم البلورات

البنية البلورية للكاسيتريت

Stalactitic-botryoidal, banded, كاسيتريت "الصفيح الخشبي"، 5.0 x 4.9 x 3.3 سم، دورانگو، المكسيك

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.

أصل الاسم

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,[بحاجة لمصدر] 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.

Close up of cassiterite crystals, Blue Tier tinfield, تازمانيا، أستراليا

انظر أيضاً

المصادر

  1. ^ Mineralienatlas
  2. ^ Handbook of Mineralogy
  3. ^ Mindat
  4. ^ Webmineral
  5. ^ Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20th ed.). New York: John Wiley and Sons. pp. 306–307. ISBN 0-471-80580-7.
  6. ^ Watt, Louise (2008-11-01). "Mining for minerals fuels Congo conflict". Yahoo News!. Yahoo! Inc. Associated Press. Retrieved 2009-09-03.
  7. ^ Polgreen, Lydia (2008-11-16). "Congo's Riches, Looted by Renegade Troops". The New York Times. Retrieved 2008-11-16.

وصلات خارجية

  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York, pp. 306-307 ISBN 0-471-80580-7.
  • Mineral galleries accessed 4-21-05.
  • Mindat accessed 4-21-05.
  • Webmineral accessed 4-21-05.
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