Archerite

Formula: (K,NH₄)H₂PO₄

Origin of name:  For Michael Archer (1945- ), Australian museum curator (mammals), Queensland Museum, Brisbane, Australia, who discovered the first specimen

Crystal system:  Tetragonal

Crystal class:  -42m

Twinning:

Unit cell: a = 7.451 Å, c = 6.792 Å

Colour:  White to colourless

Diaphaneity: Translucent

Luster:

Habit:  Tiny prismatic crystals

Hardness:  1-2

Specific gravity:  2.23

Cleavage:  None

Tenacity:

Streak:  White

Synonyms/varieties:

Comments: Found as a component in stalactites and crusts on the walls of caves containing bat guano deposits.