Color: colorless, white, gray, yellow to brown to black, violet, pink

Streak: white Synonyms/varieties:

Luster: vitreous

Habit: crystals short to prismatic, elongated along c-axis, hexagonal, horizontally striated, bent, distorted, skeletal

Hardness: 7

Specific gravity: 2.655

Cleavage: Absent

Tenacity: brittle

Twinning: very common by Dauphiné-law, less common by Japanese-law

Crystal system: hexagonal

Crystal class: 32

Diaphaneity

Unit cell: a=b = 4.91 Å, c = 5.41 Å

Comments: stable below 573°C, polymorphous with tridymite, cristobalite, coesite and stishovite