Barium sulfate, sometimes with small amounts of strontium
Variable Formula
(Ba,Sr)SO4
Color
Colorless, white, yellow, orange, red, pink, purple, brown, blue, green, gray, and black. May also be multicolored and banded.
Streak
White
Hardness
3 - 3.5
Crystal System
Orthorhombic
3D Crystal Atlas
(Click for animated model)
Crystal Forms and Aggregates
Crystals are tabular, prismatic, and as grainy, platy, and coxcomb aggregates. Individual crystals are often twinned, and can be quite large. May also be bladed, massive, nodular, fibrous, stalactitic, and as perfect rosettes. Crystals occasionally contain phantom growths.
Transparency
Transparent to opaque
Specific Gravity
4.3 - 4.6
Luster
Vitreous to pearly
Cleavage
1,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal
Fracture
Uneven
Tenacity
Brittle
Other ID Marks
Commonly fluorescent in a variety of colors; sometimes also phosphorescent.
In Group
Sulfates; Anhydrous Sulfates
Striking Features
Heaviness, hardness, and crystal habits
Environment
In sedimentary rock layers and in hydrothermal and mesothermal metal ore veins. Rarely in alteredbasalts.