Blue, Yellow, Brown, gray, Reddish, Greenish
Colorless, Blue, Violet, White, Brown, Colorless, Blue, Violet, White, rose, Brown, gray, Colorless, White, Violet, gray, Colorless, White, Violet, gray
(e.g. graphite).
Conchoidal, Brittle, Conchoidal, UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
{???} Imperfect, {???} Imperfect
Rare tabular and prismatic crystals. Usually occurs as fibrous, parallel veins that break off into cleavage fragments.