Efremovite

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

It was first described in 1989 for an occurrence in the Chelyabinsk coal basin, Southern Urals. 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  [it, and boussingaultite