Nepheline
Tawmaw (Tawhmaw; Taw Maw), Hpakant-Tawmaw Jade Tract, Hpakant Township (Hpakan; Phakant; Phakan), Mohnyin District, Kachin State, Myanmar
2.33 carats
© Brian Kosnar - Mineral Classics
Nepheline forms transparent to nearly opaque prismatic crystals, usually colourless, but can be coloured gray, red, green, brown, yellow from various impurities.
Transparent colourless material has been faceted.
| General Information | ||||||||||||||||||
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| Varieties/Types: | Elaeolite - Old name for massive, oily/greasy variety of Nepheline. | |||||||||||||||||
| Chemical Formula |
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| Physical Properties of Nepheline | ||||||||||||||||||
| Mohs Hardness | 5 to 6, Gemstones of the world (2001) More from other references | |||||||||||||||||
| Specific Gravity | 2.55 to 2.65, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||||
| Tenacity | Brittle, Gemstones (2009) | |||||||||||||||||
| Cleavage Quality | Imperfect, Gemstones (2009) | |||||||||||||||||
| Fracture | Sub-Conchoidal, Gemstones (2009) | |||||||||||||||||
| Optical Properties of Nepheline | ||||||||||||||||||
| Refractive Index | 1.529 to 1.547, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||||
| Optical Character | Uniaxial/-, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||||
| Birefringence | 0.003 to 0.005, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||||
| Colour | ||||||||||||||||||
| Colour (General) | Colourless, white, gray, greenish-gray, yellowish, reddish, blue-green, brownish. Chatoyant, Gemmological Tables (2004) More from other references | |||||||||||||||||
| Transparency | Transparent,Translucent,Opaque, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||||
| Lustre | Vitreous,Greasy, Gemstones (2009) | |||||||||||||||||
| Fluorescence & other light emissions | ||||||||||||||||||
| Fluorescence (Long-Wave UV) | Some German specimens may show a light blue and some from Ontario an orange fluorescence, Gems, Sixth Edition (2006) | |||||||||||||||||
| Crystallography of Nepheline | ||||||||||||||||||
| Crystal System | Hexagonal, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||||
| Habit | Prismatic, Gems, Sixth Edition (2006) More from other references | |||||||||||||||||
| Geological Environment | ||||||||||||||||||
| Where found: | Nepheline occurs in alkalic rocks, including nepheline syenites and pegmatites associated with them, also in gneisses., Gems, Sixth Edition (2006) | |||||||||||||||||
| Inclusions in Nepheline | ||||||||||||||||||
| Partially healed fractures, mirror-like inclusions - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 7 | ||||||||||||||||||
| Further Information | ||||||||||||||||||
| Mineral information: | Nepheline information at mindat.org | |||||||||||||||||
| Significant Gem Localities | ||||||||||||||||||
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