Crystal Angelite

Chemical Formula

CaSO₄

Composition

Calcium sulfate

Colour

Colorless, white, yellow, gray, blue, orange-red, red, pink, purple.

Streak

White to light gray

Hardness

3 - 3.5

Crystal System

Orthorhombic

Crystal Forms 
and Aggregates

Individual crystals, which are tabular and prismatic, are uncommon. Usually occurs as fibrous, parallel veins that break off into cleavage fragments, and as fan-like groupings. Also occurs grainy, massive, nodular, as rectangular cleavage fragments, and as easily cleavable crystal groupings.

Transparency

Transparent to translucent

Specific Gravity

2.9 - 3.0

Luster

Vitreous to pearly

Cleavage

2,3 - forming a cube

Fracture

Uneven to splintery

Tenacity

Brittle

Other ID Marks

Many specimens are fluorescent.

Complex Tests

Specimens that are not fluorescent may become fluorescent after heating.

In Group

Sulfates; Anhydrous Sulfates

Striking Features

Cleavage properties, crystal habits, and low specific gravity.

Environment

In sedimentary rock layers, in salt domes, and in igneous traprock.

Rock Type

Igneous, Sedimentary

Popularity (1-4)

2