Neptunite

Neptunite is a silicate mineral with the formula KNa2Li(Fe2+,Mn2+)2Ti2Si8O24. With increasing manganese it forms a series with mangan-neptunite. Watatsumiite is the variety with vanadium replacing the titanium in the formula.It was first described in 1893 for an occurrence in the Narssârssuk pegmatite of West Greenland. It is also found within natrolite veins in glaucophane schist within serpentinite in San Benito County, California, USA. The mineral is named for Neptune, Roman god of the sea because of its association with aegirine from Àgir, the Scandinavian sea-god. It also occurs in Mont Saint-Hilaire, Quebec and in the Kola Peninsula of Russia.
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General Information:
 Chemical Formula:
KNa2Li(Fe++,Mn)2Ti2Si8O24
 Composition:
(Molecular Weight = 907.69 gm)
Potassium 4.31 % K 
Sodium 5.07 % Na
Lithium 0.76 % Li
Titanium 10.55 % Ti
Manganese 3.03 % Mn
Iron 9.23 % Fe
Silicon 24.75 % Si
Oxygen 42.30 % O 
 Empirical Formula:
KNa2LiFe2+1.5Mn2+0.5Ti2Si8O24
 Locality:
Benitoite mine, San Benito, Co., California, USA.
Physical Properties:
 Cleavage:
[110] Good
 Color:
black or red.
 Density:
3.23
 Diaphaniety:
Translucent
 Habits:
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Tabular - Form dimensions are thin in one direction., Crystalline - Coarse - Occurs as well-formed coarse sized cry stals.
 Hardness:
5-6 - Between Apatite and Orthoclase
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous (Glassy)
 Streak:
brown
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