Efremovite is a rare

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...

sulfate mineral The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary mine ...

with the chemical formula: (NH₄)₂Mg₂(SO₄)₃. It is a white to gray

cubic Cubic may refer to: Science and mathematics * Cube (algebra), "cubic" measurement * Cube, a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex ** Cubic crystal system, a crystal system w ...

mineral.Handbook of Mineralogy
/ref> This anhydrous sulfate occurs as constituent in

sulfate crust Sulfate crust is a zone observed in the axial (central) parts of burning coal dumps and related sites. It is a zone built mainly by anhydrous sulfate minerals, such as godovikovite and millosevichite. The outer zone can easily be hydrated giving r ...

s of burning

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

dumps. It is

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...

and when exposed to humid air it slowly converts to the

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

form,

boussingaultite Boussingaultite is a rare ammonium magnesium hydrated sulfate mineral of the chemical formula: (NH4)2Mg(SO4)2 · 6 H2O. The formula of boussingaultite is that of Tutton's salts type. It was originally described from geothermal fields in Tuscany, ...

.Jambor J. L. and Grew E. S. 1991: New mineral names. American Mineralogist, 76, pp. 299-305 It was first described in 1989 for an occurrence in the Chelyabinsk coal basin, Southern

Urals The Ural Mountains ( ; rus, Ура́льские го́ры, r=Uralskiye gory, p=ʊˈralʲskʲɪjə ˈɡorɨ; ba, Урал тауҙары) or simply the Urals, are a mountain range that runs approximately from north to south through European ...

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

. It was named for Russian geologist Ivan Antonovich Yefremov (1907–1972). It has also been reported from several coal mining areas across Europe. It occurs in association with

native sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

, ,

mascagnite Mascagnite is a rare ammonium sulfate mineral ( N H4)2 S O4. It crystallizes in the orthorhombic system typically forming as stalactitic masses exhibiting good cleavage. It is soft (not higher than 2.5 on the Mohs Scale) and water-soluble. Opti ...

, and

References

Sulfate minerals Magnesium minerals Ammonium minerals Cubic minerals Minerals in space group 198 Minerals described in 1989 {{sulfate-mineral-stub