| General Information |
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| Chemical Formula | Michael O’Donoghue, Gems, Sixth Edition (2006) More from other references |
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| Physical Properties of Thomsonite Subgroup |
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| Mohs Hardness | 5 to 5.5Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Specific Gravity | 2.30 to 2.40Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Cleavage Quality | PerfectUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Fracture | UnevenArthur Thomas, Gemstones (2009) |
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| Optical Properties of Thomsonite Subgroup |
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| Refractive Index | 1.497 to 1.545Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Optical Character | Biaxial/+Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Birefringence | 0.015 to 0.020Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Pleochroism | NilArthur Thomas, Gemstones (2009) |
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| Dispersion | Distinct-strongArthur Thomas, Gemstones (2009) |
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| Colour |
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| Colour (General) | White, gray, yellowish, reddish. Partly with an agate-like bandingUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Transparency | Translucent,OpaqueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Lustre | SilkyHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Fluorescence & other light emissions |
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| Fluorescence (General) | Patchy brownish and whiteUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Crystallography of Thomsonite Subgroup |
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| Crystal System | OrthorhombicHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Habit | Radial fibrous structure with eye-like pattern (also banded)Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Geological Environment |
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| Where found: | Thomsonite occurs in amygdules and fractures in mafic igneous rocks, most commonly basalts.Michael O’Donoghue, Gems, Sixth Edition (2006) |
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| Further Information |
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| Mineral information: | Thomsonite Subgroup information at mindat.org |
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