Argentopentlandite

Formula:  Ag(Fe, Ni)₈S₈

Origin of name:  From silver (Latin argentum) and similarity in composition to pentlandite

Crystal system:  Cubic

Crystal class:  2/m -3 2/m

Twinning:

Unit cell: a = 10.521 Å

Colour:  Bronze-brown

Diaphaneity:  Opaque

Luster:  Metallic

Habit:  Euhedral crystals with well developed octahedral faces; massive

Hardness:  3 to 3.5

Specific gravity:  4.66 (calculated)

Cleavage:  1; {111}

Tenacity:

Streak: Reddish brown

Synonyms/varieties:

Comments: In pyrite and cubanite-chalcopyrite hydrothermal veins, and in disseminated sulphide deposits in skarn