Yellow crystal aggregates of the rare mineral magnesiostaurolite in a white contrasting matrix. From: Case Parigi, Po Valley, Dora Maira Massif, Piedmont, Italy. — Photo: David Hospital · CC BY-SA 4.0
Magnesiostaurolite
Magnesiostaurolite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mg(Mg,Li)₃(Al,Mg)₁₈Si₈O₄₄(OH)₄.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Staurolite structural group.
Key properties: Mohs hardness 7–7.5; specific gravity 3.54; White streak; Vitreous to resinous luster.
IMA symbol Mst, IMA status: approved, named in 1992.
From an ultra-high-pressure, coesite-bearing metamorphic terrane.
It is found associated with Talc, clinochlore, rutile, magnesiochloritoid, kyanite, corundum, pyrope.
The prefix, magnesio, indicates the magnesium analog of staurolite.