White crystal aggregates of the extremely rare mineral admontite from the type and only known locality worldwide in Admont (Liezen District, Styria, Austria). Admontite is a magnesium borate. — Photo: David Hospital · CC BY-SA 4.0
Admontite
A hydrated magnesium borate found in gypsum deposits, typically alongside gypsum, anhydrite, pyrite and quartz.
Intro adapted from Wikipedia (CC BY-SA).
Admontite is an IMA-recognized mineral species in the borate class, with the chemical formula MgB₆O₁₀·7H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 2–3; specific gravity 1.82; Vitreous luster; refractive index 1.473; optically biaxial.
IMA symbol Amt, IMA status: approved, named in 1978.
Found in a gypsum deposit.
It is found associated with Gypsum, anhydrite, hexahydrite, löweite, eugsterite, pyrite, quartz.
The name refers to Admont, Austria, near the original locality.