Kalsilite (KAlSiO4) is a vitreous white to the grey feldspathoidal mineral that is found in some potassium-rich lavas, such as from Chamengo Crater in Uganda. It is a rare mineral consisting of aluminosilicate of potassium. It has a relative hardness of 5.5.
General information:
- Formula: KAlSiO4
- Crystal System: Hexagonal
- Member of: Feldspathoid Group
- Type Locality: Kamengo, Gomba District, Central Region, Uganda
Fig: Kalsilite
Properties
- Cleavage: {1010} Indistinct, {0001} Indistinct
- Color: Colorless, Gray, Gray white, White.
- Density: 2.59 – 2.625, Average = 2.6
- Diaphaneity: Transparent to Translucent
- Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments.
- Hardness: 6 – Orthoclase
- Luster: Vitreous – Greasy
- Streak: white
Occurrence: In the groundmass of some potassium-rich and silica-de¯cient lavas and tu®s; rare in syenites; may be formed by the breakdown of silica-rich leucite in alkalic ultrama¯c rocks; from a granulite-facies emery deposit.
Association: Olivine, melilite, clinopyroxene, phlogopite, nepheline, leucite.
