Ammonioleucite

Formula:  (NH₄,K)AlSi₂O₆

Origin of name:  From ammonia in its chemical composition and leucite

Crystal system:  Tetragonal

Crystal class:  4/m

Twinning: common, repeated on {110}

Unit cell: a = 13.214 Å, c = 13.713 Å

Colour:  White

Diaphaneity: Translucent

Luster:  Resinous to vitreous

Habit:  Submicroscopic crystal aggregates forming surface layers replacing analcime

Hardness: 5.5-6

Specific gravity:  2.29

Cleavage:  None

Tenacity:

Streak: White

Synonyms/varieties:

Comments: Found in veinlets, fractures and cavities in hydrothermally altered crystalline schist, as powdery pseudomorphous replacement of analcime crystals