Grossite

Grossite is a calcium aluminium oxide mineral with formula CaAl₄O₇. It is a colorless to white vitreous mineral which crystallizes in the monoclinic crystal system.^[3][4]

Grossite
General
Category	Oxide minerals
Formula	CaAl4O7
IMA symbol	Gss[1]
Strunz classification	4.CC.15
Dana classification	07.03.02.01
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/c
Unit cell	a = 12.94, b = 8.91 c = 5.44 [Å]; β = 107.01°; Z = 4
Identification
Color	Colorless to white
Crystal habit	Lathlike or subhedral rounded grains in polycrystalline aggregates rimmed by melilite (in meteorites)
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Specific gravity	2.88
Optical properties	Biaxial (+)
Refractive index	nα = 1.618 nβ = 1.618 nγ = 1.652
Birefringence	δ = 0.034
2V angle	Measured: 15°
References	[2][3][4]

Grossite was first described 1994 for an occurrence in the Hatrurim Formation of Israel. It was named for Shulamit Gross (1923–2012) of the Geological Survey of Israel.^[2][4]

It occurs within high temperature metamorphosed impure limestone of the Hatrurim Formation and also within calcium-aluminium rich inclusions in chondritic meteorites. Associated minerals in the Hatrurium include brownmillerite, mayenite and larnite. In meteorites it occurs with perovskite, melilite, hibonite, spinel and calcium rich pyroxene.^[2]

See also

• Glossary of meteoritics