Pink crystal aggregates of the very rare ammonium Mg sulphate mineral boussingaultite from a little known locality in Ventura Co., California (South Mountain, Santa Paula, Ventura County, California, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Boussingaultite
A rare ammonium-magnesium sulfate hydrate of the Tutton's-salt type.
Intro adapted from Wikipedia (CC BY-SA).
Boussingaultite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (NH₄)₂Mg(SO₄)₂·6H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/a). It is a member of the Picromerite structural group.
Key properties: Mohs hardness 2; specific gravity 1.722; Silky luster; optically biaxial.
IMA symbol Bsg, grandfathered status — known before the IMA’s founding, named in 1864.
A rare sublimate formed under fumarolic conditions.
The mineral was named to honor Professor Jean-Baptiste Joseph Dieudonné Boussingault (1802–1887), French chemist, Lyon University, Lyon, France.