Adelite

Formula:  CaMg(AsO₄)(OH)

Origin of name:  from Greek for indistinct (not transparent)

Crystal system:  Orthorhombic

Crystal class: 222

Twinning:

Unit cell: a = 7.43 Å, b = 8.85 Å, c = 5.88 Å

Colour:  Colorless, gray to bluish gray, yellow to yellowish gray, pale green

Diaphaneity: Translucent to transparent

Luster:  Resinous

Habit:  Crystals rare, elongated or tabular; commonly massive

Hardness:  5

Specific gravity:  3.73

Cleavage:  None

Tenacity: Brittle

Streak: White

Synonyms/varieties:

Comments: Member of the adelite group. Found as a rare mineral in metamorphosed Fe-Mn orebody; on willemite-franklinite ore from a metamorphosed stratiform zinc orebody.