Lazurite

Lazurite
Lazurite, Ladjuar Medam (Lajur Madan; Lapis-lazuli Mine), Sar-e-Sang District, Koksha Valley (Kokscha; Kokcha), Badakhshan (Badakshan; Badahsan) Province, Afghanistan
General
CategoryTectosilicate
Formula
(repeating unit)
(Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)]
IMA symbolLzr[1]
Strunz classification9.FB.10
Crystal systemIsometric
Crystal classHextetrahedral (43m)
H-M symbol: (4 3m)
Space groupP43n
Unit cella = 9.09 Å; Z = 2
Identification
ColorDeep blue, azure, violet-blue, greenish blue
Crystal habitCrystals occur as dodecahedra, or rarely cubes; granular, disseminated, or massive
CleavageImperfect on {110}
FractureUneven
TenacityBrittle
Mohs scale hardness5–5.5
LusterVitreous
DiaphaneityTranslucent to opaque
Specific gravity2.38–2.45
Optical propertiesIsotropic; anomalously anisotropic
Refractive index1.502–1.522
Fusibility3.5
SolubilitySoluble in HCl
References[2][3][4][5][6]

Lazurite, old name Azure spar[7]: 14  is a tectosilicate mineral with sulfate, sulfur and chloride with formula (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)]. 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.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ Mindat with location data
  4. ^ Webmineral data
  5. ^ Hurlbut, Cornelius S. and Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, p. 459 ISBN 0-471-80580-7
  6. ^ "Mineralogical Society of America" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2011-03-08.
  7. ^ Krivovichev V. G. Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. (in Russian)