M393 -

Potassium Aluminum silicate. Hardness 5-1/2 to 6. Fracture - conchoidal, brittle. Tetragonal, usually in pseudo isometric trapezohedal crystals; also rounded, disseminated grains.

Leucite develops in basalt of volcanic rocks and is usually associated with olivine and labradorite. Leucite is used as a potash-fertilizer. Czech Republic.