Lazurite

Lazurite
Lazurite
	Lazurite, Ladjuar Medam (Lajur Madan; Lapis-lazuli Mine), Sar-e-Sang District, Koksha Valley (Kokscha; Kokcha), Badakhshan (Badakshan; Badahsan) Province, Afghanistan
General
Category	Tectosilicate
Formula; (repeating unit)	(Na,Ca)8[(S,Cl,SO4,OH)2\|(Al6Si6O24)]
IMA symbol	Lzr
Strunz classification	9.FB.10
Crystal system	Isometric
Crystal class	Hextetrahedral (43m) ; H-M symbol: (4 3m)
Space group	P43n
Unit cell	a = 9.09 Å; Z = 2
Identification
Color	Deep blue, azure, violet-blue, greenish blue
Crystal habit	Crystals occur as dodecahedra, or rarely cubes; granular, disseminated, or massive
Cleavage	Imperfect on {110}
Fracture	Uneven
Tenacity	Brittle
Mohs scale hardness	5–5.5
Luster	Vitreous
Diaphaneity	Translucent to opaque
Specific gravity	2.38–2.45
Optical properties	Isotropic; anomalously anisotropic
Refractive index	1.502–1.522
Fusibility	3.5
Solubility	Soluble in HCl
References

Lazurite 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.

Mineral

Lazurite is a deep‐blue to greenish‐blue. The colour is due to the presence of S⁻
₃ anions.^[7] It has a Mohs hardness of 5.0 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 on Wolfgang Franz von Kobell's fusibility scale, and soluble in HCl. It commonly contains or is associated with grains of pyrite.

Lazurite is a product of contact metamorphism of limestone and is typically associated with calcite, pyrite, diopside, humite, forsterite, hauyne and muscovite.^[2]

Other blue minerals, such as the carbonate azurite and the phosphate lazulite, may be confused with lazurite, but are easily distinguished with careful examination. At one time, lazurite was a synonym for azurite.^[5]

Lazurite was first described in 1890 for an occurrence in the Sar-e-Sang District, Koksha Valley, Badakhshan Province, Afghanistan.^[3] It has been mined for more than 6,000 years in the lapis lazuli district of Badakhshan. It has been used as a pigment in painting and cloth dyeing since at least the 6th or 7th century.^[8] It is also mined at Lake Baikal in Siberia; Mount Vesuvius; Burma; Canada; and the United States.^[8] The name is from the Persian lajvard for blue.^[9]

Structure

Lazurite and hauyne seem to have the same structure and both are sulfate-dominant minerals.^[10] Lazurite is a pigment (opalescent) and has a bright blue streak (especially as a component of the semiprecious stone lapis lazuli). Many hauynes have a white or pale blue streak and are translucent. The difference might be a consequence of the redox state (sulfate to sulfide ratio).^[7]^[11]

References

^ 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.
^ ^a ^b Handbook of Mineralogy
^ ^a ^b Mindat with location data
^ Webmineral data
^ ^a ^b Hurlbut, Cornelius S. and Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, p. 459 ISBN 0-471-80580-7
^ "Mineralogical Society of America" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2011-03-08.
^ ^a ^b Tauson VL, Sapozhnikov AN (2003). "On the nature of lazurite coloring" (PDF). Zapiski Vserossijskogo Mineralogicheskogo Obshchestva (in Russian). 132 (5): 102–107.
^ ^a ^b Eastaugh, Nicholas; et al. (2004). The Pigment Compendium: Optical Microscopy of Historical Pigments. Oxford: Elsevier Butterworth-Heinemann. p. 219. ISBN 0-7506-4553-9.
^ "Tile fragment". Victoria and Albert Museum. Retrieved 11 January 2020.
^ Moore, T.P.; Woodside, R. W. M. (2014). "The Sar-e-Sang Lapis Mines". Mineralogical Record. 45 (3): 281–336.
^ Hettmann K, Wenzel T, Marks M, Markl G (2012). "The sulfur speciation in S-bearing minerals: New constraints by a combination of electron microprobe analysis and DFT calculations with special reference to sodalite-group minerals". American Mineralogist. 97 (10): 1653–1661. Bibcode:2012AmMin..97.1653H. doi:10.2138/am.2012.4031. S2CID 54921328.

External links

Media related to Lazurite at Wikimedia Commons

[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.

[HBM-2] Handbook of Mineralogy

[Mindat-3] Mindat with location data

[Webmin-4] Webmineral data

[Klein-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.

[Sapozhnikov-7] Tauson VL, Sapozhnikov AN (2003). "On the nature of lazurite coloring" (PDF). Zapiski Vserossijskogo Mineralogicheskogo Obshchestva (in Russian). 132 (5): 102–107.

[Eastlaugh-8] Eastaugh, Nicholas; et al. (2004). The Pigment Compendium: Optical Microscopy of Historical Pigments. Oxford: Elsevier Butterworth-Heinemann. p. 219. ISBN 0-7506-4553-9.

[VandA-9] "Tile fragment". Victoria and Albert Museum. Retrieved 11 January 2020.

[10] Moore, T.P.; Woodside, R. W. M. (2014). "The Sar-e-Sang Lapis Mines". Mineralogical Record. 45 (3): 281–336.

[11] Hettmann K, Wenzel T, Marks M, Markl G (2012). "The sulfur speciation in S-bearing minerals: New constraints by a combination of electron microprobe analysis and DFT calculations with special reference to sodalite-group minerals". American Mineralogist. 97 (10): 1653–1661. Bibcode:2012AmMin..97.1653H. doi:10.2138/am.2012.4031. S2CID 54921328.

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Lazurite

Mineral

Structure

See also

References

External links

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