Grossite: Properties and Occurrences

Grossite is a calcium aluminum oxide mineral with formula CaAl4O7. It is a monoclinic-prismatic mineral containing aluminum, calcium, and oxygen. It is a colorless to white vitreous mineral which crystallizes in the monoclinic crystal system.

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.

General Information

  • Category: Oxide minerals
  • Formula: CaAl4O7
  • Crystal system: Monoclinic
  • Crystal class: Prismatic (2/m) (same H-M symbol)

Fig: Grossite – calcium aluminum oxide mineral


  • Color: Colorless to white
  • Luster: Vitreous
  • Streak: White
  • Diaphaneity: Transparent
  • Specific gravity: 2.88
  • Optical properties: Biaxial (+)


It occurs within high temperature metamorphosed impure limestone of the Hatrurim Formation and also within calcium-aluminum-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.

Association: Brownmillerite, mayenite, larnite (Hatrurim Formation, Israel); perovskite, melilite, hibonite, spinel, calcian pyroxene (meteorites).


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