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Lazurite



Lazurite

A lazurite specimen
General
CategoryMineral
Chemical formulatectosilicate (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2
Identification
ColorDeep blue to greenish blue
Crystal systemIsometric
Mohs Scale hardness5-5.5
Lustertranslucent
Refractive index1.5
Specific gravity2.4
Fusibility3.5
SolubilitySoluble in HCl

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.

Additional recommended knowledge

Lazurite is a deep blue to greenish blue. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 2.4. It is translucent with a refractive index of 1.50. It is fusible at 3.5 and soluble in HCl. It commonly contains or is associated with grains of pyrite.

Lazurite is a product of contact metamorphism of limestone and typically is associated with calcite, pyroxenes, and pyrite.

Other blue minerals such as the carbonate azurite and the phosphate lazulite may be confused with lazurite, but are easily distinguished with careful examination. Lazurite at one time was used as a synonym for azurite.

Lazurite was first described in 1890 from the lapis lazuli district of Badakhshan, Afghanistan. The name is from the Persian lazward for blue.

References

  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, ISBN 0-471-80580-7
  • Mindat with location data
  • Mineral galleries
  • Webmineral data
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Lazurite". A list of authors is available in Wikipedia.
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