Efremovite

Rare ammonium sulfate mineral
(repeating unit)(NH4)2Mg2(SO4)3IMA symbolEfr[1]Strunz classification7.AC.10Crystal systemCubicCrystal classTetartoidal (23)
H-M symbol: (23)Unit cella = 9.99 Å; Z = 2IdentificationColorWhite to grayCrystal habitEquant grains and crustsCleavageNoneFractureUnevenMohs scale hardness2LusterVitreousDiaphaneityTransparent to nearly opaqueSpecific gravity2.52 (calculated)Optical propertiesIsotropicRefractive indexn = 1.550Alters toReadily hygroscopicReferences[2][3][4]

Efremovite is a rare ammonium sulfate mineral with the chemical formula: (NH4)2Mg2(SO4)3. It is a white to gray cubic mineral.[4] This anhydrous sulfate occurs as constituent in sulfate crusts of burning coal dumps. It is hygroscopic and when exposed to humid air it slowly converts to the hydrate form, boussingaultite.[5][6]

It was first described in 1989 for an occurrence in the Chelyabinsk coal basin, Southern Urals, Russia. It was named for Russian geologist Ivan Antonovich Yefremov (1907–1972). It has also been reported from several coal mining areas across Europe.[3] It occurs in association with native sulfur, kladnoite [it], mascagnite, and boussingaultite.[4]

References

  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. ^ Efremovite, Webmineral.com
  3. ^ a b Efremovite, Mindat.org
  4. ^ a b c Handbook of Mineralogy
  5. ^ Chesnokov B. V. and Shcherbakova E. P. 1991: Mineralogiya gorelykh otvalov Chelyabinskogo ugolnogo basseina - opyt mineralogii tekhnogenesa. Nauka, Moscow
  6. ^ Jambor J. L. and Grew E. S. 1991: New mineral names. American Mineralogist, 76, pp. 299-305


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