Argutite

Formula:  GeO₂

Origin of name:  After locality; Argut Plain, France

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m (synthetic)

Twinning: occasionally twinned on {101}

Unit cell: a = 4.398 Å, c = 2.863 Å (synthetic)

Colour: Grayish black

Diaphaneity: Semi-transparent

Luster: Vitreous, adamantine

Habit:  Euhedral to subhedral prismatic microscopic grains

Hardness: 6-7

Specific gravity:  6.28 (calculated)

Cleavage:  None

Tenacity:

Streak:

Synonyms/varieties:

Comments: Member of the rutile group. Observed in a zinc deposit formed in metamorphosed lower Paleozoic sediments.