Neptunite
Neptunite is named after Neptune, Roman god of the sea, because it was found with
aegirine, which was named after Aegir, the Scandinavian sea god.
Neptunite forms translucent or opaque black or very dark red prismatic crystals with square cross-sections.
The crystals of Neptunite show piezoelectricity.
General Information |
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Chemical Formula | Michael O’Donoghue, Gems, Sixth Edition (2006) |
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Physical Properties of Neptunite |
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Mohs Hardness | 5 to 6Walter Schumann, Gemstones of the world (2001) More from other references |
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Specific Gravity | 3.19 to 3.23Walter Schumann, Gemstones of the world (2001) More from other references |
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Tenacity | BrittleAnthony et al, Handbook of Mineralogy (2001) |
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Cleavage Quality | PerfectMichael O’Donoghue, Gems, Sixth Edition (2006) |
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Fracture | ConchoidalAnthony et al, Handbook of Mineralogy (2001) |
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Optical Properties of Neptunite |
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Refractive Index | 1.692 to 1.734Michael O’Donoghue, Gems, Sixth Edition (2006) |
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Optical Character | Biaxial/+Michael O’Donoghue, Gems, Sixth Edition (2006) |
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Birefringence | 0.029 to 0.045Michael O’Donoghue, Gems, Sixth Edition (2006) |
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Pleochroism | Pale yellow - yellow-orange - orange to red-brownAnthony et al, Handbook of Mineralogy (2001) |
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Dispersion | ExtremeAnthony et al, Handbook of Mineralogy (2001) |
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Colour |
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Colour (General) | Black or very dark redMichael O’Donoghue, Gems, Sixth Edition (2006) |
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Transparency | Translucent,OpaqueWalter Schumann, Gemstones of the world (2001) More from other references |
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Lustre | VitreousWalter Schumann, Gemstones of the world (2001) More from other references |
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Crystallography of Neptunite |
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Crystal System | MonoclinicMichael O’Donoghue, Gems, Sixth Edition (2006) |
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Habit | Prismatic crystals with square cross-sectionsMichael O’Donoghue, Gems, Sixth Edition (2006) |
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Geological Environment |
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Where found: | Occurs in natrolite veins cutting a glaucophane schist in a serpentinite bodyMichael O’Donoghue, Gems, Sixth Edition (2006) |
Further Information |
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Mineral information: | Neptunite information at mindat.org |
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Significant Gem Localities |
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| USA | |
| Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 433 |
| Wise, W.S & Gill, R.H. (1977): Minerals of the Benitoite Gem mine. Mineralogical Record 8, 442-452 |
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