Fassaite

Fassaite
Fassaite from Val di Fassa
General
Category	Mineral
Formula (repeating unit)	Ca(Mg,Fe,Al)(Si,Al)2O6
Identification
Color	light-dark green, black
Crystal habit	prismatic, short, plane
Crystal system	Monoclinic prismatic
Mohs scale hardness	6
Streak	greenish-white
Specific gravity	2.9-3.3

Fassaite is a variety of augite with a very low iron content, Ca(Mg,Fe,Al)(Si,Al)₂O₆.^[1] It is named after the Fassa Valley, Italy.

It is thought to be a contact mineral formed at high temperature on the interface between volcanic rocks and limestone. It is also reported in meteorites.^[2]

References

1. Mindat
2. Simon, S. B. and L. Grossman, A comparative study of melilite and fassaite in Types B1 and B2 refractory inclusions, Geochimica et Cosmochimica Acta 70 (2006) 780–798

• Schumann, Walter (1991). Mineralien aus aller Welt. BLV Bestimmungsbuch (2 ed.). p. 223. ISBN 3-405-14003-X.