Cassiterite

Big Photo

Bolivia
3.50 carats
© Rarestone.com

The name derived from Greek "kassiteros" - tin, for its composition.

Facet rough is uncommon but can yield gems of exceptional fire, because of its high lustre and dispersion. With a hardness of 7, approximately the same as that of the quartz gems, cassiterite is occasionally marketed for wearable jewelry in Bolivia ("Andean diamond"), but is normally restricted to rare gem collections.

Although cassiterite is a common mineral, being the main ore of tin, it's crystals are usually black or opaque brown and of no use as a gemstone. Only a few localities yield gem quality material, which ranges from colorless to yellow to pale brown. Bolivia has traditionally been the main source of gem rough, with the Viloco mine there being the only one of Bolivia's 300 or so tin mines that occasionally yields transparent crystals. However in the late 1990s, Russia and China yielded larger transparent crystals than Bolivia. Other sporadic sources of facetting grade cassiterite include Nigeria and Namibia.

The "wood tin" variety of cassiterite is massive, tough, internally micro-fibrous, opaque, and finely colour banded, being related to crystallized cassiterite the same way agate is related to quartz. As with cassiterite crystals, wood tin generally is found in black or brown tones, but it is used for cabochons when it is found (rarely) in more attractive colors like red, pink and creamy white. Mexico and Bolivia are the main source countries for ornamental grades of wood tin.

Cassiterite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 

Cassiterite Gemstones by Size

This table shows distribution of Cassiterite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.17 cts
Heaviest:63.5 cts
Average:7.86 cts
Total photos:20
Do you have a larger Cassiterite? Why not upload a photo?
0.17ct to 6.50ct6.50ct to 12.84ct12.84ct to 19.17ct19.17ct to 25.50ct25.50ct to 31.84ct31.84ct to 38.17ct38.17ct to 44.50ct44.50ct to 50.83ct50.83ct to 57.17ct57.17ct to 63.50ct
General Information
Varieties/Types:
Wood Tin - A massive variety of Cassiterite displaying coloured bands resembling Agate.
Chemical Formula
SnO
 
2
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Photos of natural/un-cut material from mindat.org
Physical Properties of Cassiterite
Mohs Hardness6 to 7
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Specific Gravity6.86 to 7.03
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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TenacityBrittle
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityIndistinct
Walter Schumann, Gemstones of the world (2001)
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FractureConchoidal
Arthur Thomas, Gemstones (2009)
Optical Properties of Cassiterite
Refractive Index1.990 to 2.105
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterUniaxial/+
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.096 to 0.098
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) DoublingMore from other references
PleochroismWeak to strong; green-yellow, brown, red-brown
Walter Schumann, Gemstones of the world (2001)
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Dispersion0.071
Michael O’Donoghue, Gems, Sixth Edition (2006)
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ChatoyancyYes
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Colour
Colour (General)Common brown color banding
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreAdamantine
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Fluorescence & other light emissions
Fluorescence (General)Inert
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Cassiterite
Crystal SystemTetragonal
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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HabitForms prismatic crystals characterized by square cross-section and steep pyramidal forms; geniculate twins are common.
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Geological Environment
Where found:Cassiterite occurs in medium- to high-temperature hydrothermal veins.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Cassiterite information at mindat.org
Significant Gem Localities
Bolivia
 
  • La Paz Department
    • Loayza Province
Myanmar
 
  • Mandalay Region (Mandalay Division)
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Kyatpyin North
Ted Themelis (2008) Gems & mines of Mogok
        • Kyauk-Pyat-That
Ted Themelis (2008) Gems & mines of Mogok
    • Yamethin District
Ted Themelis (2008) Gems & mines of Mogok
Namibia
 
  • Kunene Region
    • Damaraland District
Sri Lanka
 
  • Sabaragamuwa Province
    • Ratnapura District
      • Ratnapura
USA
 
  • Montana
    • Lewis and Clark Co.
      • East Helena
        • Eldorado Bar
E.Ya. Kievlenko (2003) Geology of gems, p. 70
Copyright © Jolyon & Katya Ralph 1993-2017. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.