Chemical Formula

(Na,Ca)1(Si,Al)4O8

Hardness (Mohs)

6

Crystal System

Triclinic

Streak

White

Luster

Vitreous to pearly, sometimes metallic due to the labradorescence.

Diaphaneity

Transparent to translucent

Color

Typically gray, but what's most distinctive is its strong play of color (labradorescence), which can show brilliant metallic tints of blue, green, yellow, orange, and red. The body color itself can also be colorless, white, or brownish.

Crystal Habit / Mode of Occurrence

Commonly occurs as coarse, often twinned, crystals within intrusive igneous rocks. Can also be massive. Well-formed crystals are often tabular.