| General Information |
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| A variety or type of: | Quartz |
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| Chemical Formula | Walter Schumann, Gemstones of the world (2001) |
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| Amethyst Treatments |
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| Heat treatment between 878 - 1382 degrees F (470 - 750 degrees C) produces light yellow, red-brown, green, or colorless varieties. The original color an be restored by X-ray radiation. - Gemstones of the world, Walter Schumann, 2001, p 118 |
| Physical Properties of Amethyst |
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| Mohs Hardness | 7Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Specific Gravity | 2.65Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Tenacity | BrittleWalter Schumann, Gemstones of the world (2001) |
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| Cleavage Quality | NoneWalter Schumann, Gemstones of the world (2001) |
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| Fracture | ConchoidalWalter Schumann, Gemstones of the world (2001) |
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| Optical Properties of Amethyst |
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| Refractive Index | 1.544 to 1.553Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Birefringence | 0.009Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Pleochroism | Weak: (gray)-purple - reddish-purpleHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Dispersion | 0.013Walter Schumann, Gemstones of the world (2001) |
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| Colour |
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| Colour (General) | Purple, violet, pale red-violetWalter Schumann, Gemstones of the world (2001) More from other references |
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| Colour (Daylight) | Some amethysts lose some color in daylight.Walter Schumann, Gemstones of the world (2001) |
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| Colour (Chelsea Filter) | ReddishHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Causes of Colour | Violet to purple, O2+→Fe4+ charge transfer, due to irradiation.W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) |
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| Transparency | Transparent,TranslucentUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Fluorescence & other light emissions |
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| Fluorescence (General) | Inert to weak greenish or bluishHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Crystallography of Amethyst |
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| Crystal System | TrigonalUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Habit | Hexagonal prismsWalter Schumann, Gemstones of the world (2001) |
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| Geological Environment |
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| Where found: | Found in geodes in alluvial deposits.Walter Schumann, Gemstones of the world (2001) |
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| Inclusions in Amethyst |
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Typical "zebra stripe" pattern, 2 phase inclusions in veil-like pattern - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 7
Healing cracks ("tiger-stripes"), Brazilian law twinning - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 9 |
| Further Information |
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| Mineral information: | Amethyst information at mindat.org |
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| Significant Gem Localities |
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| | | Bolivia | | |
| Laurs (2001, 2010) | |
| Laurs (2001, 2010) | |
| Laurs (2001, 2010) | | Brazil | | |
| Couto (2000) | |
| Priester (1999) | |
| Rocks & Min.:5:131. | |
| Rocks & Min.: 5:131. | |
| Rocks & Min.:5:131. | |
| Balzer (1999) | |
| | |
| R. Batista and D. Epstein (2000) | | Cambodia | | |
| Ngu and Ngoc (1986) | | Canada | | |
| Garland (2004) | |
| Sinkankas (1997) | | India | | |
| S. Fernandes (1999) | | Kenya | | |
| Henn and Milisenda (2001) | | Madagascar | | |
| Aurisicchio et al. (1999) | |
| Pezzotta (1999) | | Mexico | |
- Eduardo Neri Municipality
| Ontiveros et al. (2004) | |
| Ontiveros et al. (2004) | | Myanmar | | |
| Ted Themelis (2008) Gems & mines of Mogok | |
| Ted Themelis (2008) Gems & mines of Mogok | |
| Ted Themelis (2008) Gems & mines of Mogok | | Namibia | | |
| Michelou (2006) | | Nigeria | | |
| Laurs and Koivula (2003) | | Russia | | |
| P. Lyckberg (2009) | |
| V. Bukanov (1999) | |
| V. Bukanov (1999) | | South Korea | |
- South Gyeongsang Province
| Yang et al. (2001) | | Uruguay | | |
| Gilg et al. (2003) | |
| mindat.org | | USA | | |
| Lowell and Koivula (2004) | |
| Laurs (2005) |
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