Lazurite

n. dark blue mineral which is found in the semi-precious gemstone lapis lazuli

Lazurite is a tectosilicate mineral with sulfate, sulfur and chloride with formula: (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2. It is a feldspathoid and a member of the sodalite group. Lazurite crystallizes in the isometric system although well formed crystals are rare. It is usually massive and forms the bulk of the gemstone lapis lazuli.
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n. lazurite, mineral which forms dark blue crystals

n. lazurite, dark blue mineral which is found in the semi-precious gemstone lapis lazuli, azure-blue mineral

General Information:
 Chemical Formula:
Na3Ca(Al3Si3O12)S
 Composition:
(Molecular Weight = 498.31 gm)
Sodium 13.84 % Na
Calcium 8.04 % Ca
Aluminum 16.24 % Al
Silicon 16.91 % Si
Sulfur 6.43 % S 
Oxygen 38.53 % O 
 Empirical Formula:
Na3CaAl3Si3O12S
 Locality:
District of Badakhshan, Afghanistan.
 Name Origin:
From the Persian lazward - "blue."
Physical Properties:
 Cleavage:
[110] Imperfect
 Color:
blue, azure blue, violet blue, or greenish blue.
 Density:
2.38 - 2.42, Average = 2.4
 Diaphaniety:
Translucent
 Habits:
Massive - Granular - Common texture observed in granite and other igneous rock., ,
 Hardness:
5.5 - Knife Blade
 Luminescence:
Fluorescent.
 Luster:
Vitreous - Dull
 Streak:
light blue
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