Neptunite
Real mineral · very rare · KNa₂Li(Fe++,Mn)₂Ti₂Si₈O₂₄
Lustrous black prisms grown in natrolite veins cutting serpentinite, and the constant companion of benitoite at the one Californian locality that made both famous. Named after Neptune, brother of Ægir.
Identity
- Formula
- KNa₂Li(Fe++,Mn)₂Ti₂Si₈O₂₄
- Chemical class
- silicate
Crystallography
- Crystal system
- monoclinic
- Habits
- prismatic, tabular
- Fracture
- conchoidal
Physical properties
- Mohs hardness
- 5.5
- Density
- 3.23 g/cm³
- Luster
- vitreous
- Colors
- black, red
- Streak
- brown
- Transparency
- translucent
Geology
- Origins
- hydrothermal, metamorphic
- Host rocks
- serpentinite, natrolite vein
- Associated minerals
- Benitoite, Natrolite, Joaquinite
- Geography
- USA, Greenland, Russia
Classification
- Rarity
- very rare
- Gem quality
- Yes
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