Prehnite
Prehnite is named after Dutch Colonel Hendrik Von Prehn, and was first described in 1789 for an occurrence in Haslach, Harzburg and Oberstein, Germany.
Individual crystals are rare. Faceted gems are seldom fully transparent and don't show "fire". Prehnite is usually cut into cabochons or carved.
Extensive deposits of gem quality prehnite occur near Wave Hill Station in the central Northern Territory, of Australia.
Prehnite cat's is known.
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 Prehnite |
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Mohs Hardness | 6 to 6.5Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Specific Gravity | 2.80 to 2.95Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Tenacity | BrittleHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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Cleavage Quality | GoodWalter Schumann, Gemstones of the world (2001) More from other references |
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Fracture | UnevenWalter Schumann, Gemstones of the world (2001) More from other references |
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Optical Properties of Prehnite |
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Refractive Index | 1.611 to 1.673Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Optical Character | Biaxial/+Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Birefringence | 0.021 to 0.039Walter Schumann, Gemstones of the world (2001) More from other references |
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Pleochroism | AbsentWalter Schumann, Gemstones of the world (2001) More from other references |
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Dispersion | NoneWalter Schumann, Gemstones of the world (2001) More from other references |
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Chatoyancy | YesUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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Colour |
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Colour (General) | Oily yellowish-(greenish)Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Transparency | TranslucentHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Lustre | Vitreous,PearlyHerve 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) | NoneWalter Schumann, Gemstones of the world (2001) |
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Crystallography of Prehnite |
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Crystal System | OrthorhombicHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Habit | Radiating fibrous aggregateUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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Geological Environment |
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Where found: | Occurs as a secondary or hydrothermal mineral in veins or cavities in mafic volcanic rocks or in granite gneisses or syenitesMichael O’Donoghue, Gems, Sixth Edition (2006) |
Further Information |
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Mineral information: | Prehnite information at mindat.org |
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Significant Gem Localities |
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| Australia | |
| Gemstones of the world, W. Schumann, 2001, p.188 | | Canada | |
| Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 440 | | USA | |
| Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 440 |
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