Barite

Chemical Formula : BaSO₄
Hardness : 3-3.5
Cleavage : Three; one perfect, one good, one distinct.
Luster : Vitreous to pearly
Color : Colorless to white with casts of yellow, brown red, gray, green or blue.
Streak : White
Density : 4.48
Diagnostic Features and Trivia : While commonly resembling quartz in non-crystalline specimens, barite is easily discernible by its greater specific gravity.
Crystal System and Habit : Orthorhombic; commonly tabular {001}, but also prismatic.
Twinning : None
Polymorphs : None
Index of Refraction : alpha=1.634-1.637; beta=1.633-1.639; gamma=1.646-1.649