Genthelvite

Formula:  Zn₄Be₃(SiO₄)₃S

Origin of name:  For F. Genth, German-American chemist

Crystal system:  Cubic

Crystal class:  -43m

Twinning:

Unit cell: a = 8.121 Ǻ

Colour:  Colourless, white, yellowish, bluish green, green

Diaphaneity:

Luster:  Vitreous

Habit:  Crystals tetrahedral; rounded aggregates

Hardness:  6 to 6.5

Specific gravity:  3.62

Cleavage:  None

Tenacity:  Uneven; brittle

Streak: 

Synonyms/varieties:

Comments:  Series with danalite and with helvite