Black sharp crystal of magnesiochloritoid from Austria (Hohe Tauern, Salzburg, Austria) in matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Magnesiochloritoid
Magnesiochloritoid is an IMA-recognized mineral species in the silicate class, with the chemical formula MgAl₂O(SiO₄)(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/c). It is a member of the Chloritoid structural group.
Key properties: Mohs hardness 6.5; specific gravity 3.25; optically biaxial.
IMA symbol Mcld, IMA status: approved, named in 1963.
Found in metapelites and related rocks within high-grade blueschist ro cks; stable under metamorphic conditions of near 500 ± C and 18 kbar.
It is found associated with Talc, chlorite, muscovite, quartz, kyanite, garnet, omphacite, rutile, apatite.
The name refers to magnesium in its composition and its relation to chloritoid.