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Mineralpedia Details for Neptunite

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Neptunite

Neptunite

Named after the Roman mythological god of the sea, Neptune due to its association at the type locality with aegerine which derived its name from Ægir, who was the Scandinavian mythological god of the sea. Neptunite is found in localities in Greenland, Russia, Mongolia, Tajikistan, Ireland, Canada, the USA, and Australia among only a couple others. At one if its United States localities in California, Neptunite occurs “in natrolite veins cutting a glaucophane schist inclusion in a serpentinite body.” Neptunite is piezoelectric and will generate a charge in response to pressure.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/neptunite.pdf

Formula
KNa2LiFe2+2Ti2Si8O24 
Crystal System
Monoclinic 
Crystal Habit
Prismatic, Tabular, Crystalline - Coarse 
Cleavage
Good, None, None 
Luster
Vitreous (Glassy) 
Color
black, red 
Streak
brown 
Class
Monoclinic - Domatic 
Fracture
Conchoidal 
Hardness
5-6 
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Neptunite from Gem mine, San Benito Co., California, United States

Neptunite
            from Gem mine, San Benito Co., California, United States

Black, vitreous, long prismatic crystals with complex terminations to 2.2cm exposed from white Natrolite matrix.

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Neptunite from Darai-Pioz Glacier, Alayskiy Range, Tien Shan Mts, Tajikistan

Neptunite
            from Darai-Pioz Glacier, Alayskiy Range, Tien Shan Mts, Tajikistan

Deep reddish brown crystals to 2cm. Comes from the Fersman museum. Note labels in prov. tab.

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