Fettelite

Formula:  Ag₂₄HgAs₅S₂₀

Origin of name:   For Mr. M. Ferrel, German collector

Crystal system:  Hexagonal

Crystal class:  Unknown

Twinning:

Unit cell: 

Colour:  Dark violet, scarlet

Diaphaneity:

Luster:  Submetallic to adamantine

Habit:  Hexagonal flakes up to 10 x 200 µm forming clusters, and compact subparallel aggregate of hexagonal tablets to 50 µm thick

Hardness:  4

Specific gravity:  6.29

Cleavage:  1; {0001} perfect

Tenacity: 

Streak:  Dark vermilion

Synonyms/varieties:

Comments: