Green crystals of the rare mineral meta-alunogen from South Dakota, USA (Runge Mine, Edgemont, Fall River County, South Dakota, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Meta-alunogen
Meta-alunogen is an IMA-recognized mineral species in the sulfate class, with the chemical formula Al₂(SO₄)₃·14H₂O.
Key properties: specific gravity 2.85; Waxy to pearly luster; optically biaxial.
IMA symbol Malg, IMA status: questionable, named in 1942.
An uncommon mineral formed by dehydration of alunogen; found in sulfate-rich hydrothermal deposits and geothermal fields.
It is found associated with Alunogen, pickeringite, halotrichite, mirabilite, kalinite, gypsum.
The name refers to meta, indicating a lower hydrate, and alunogen.