Balkanite

Formula:  Cu₉Ag₅HgS₈

Origin of name:  After locality; Vratsa, Balkan Peninsula, Bulgaria

Crystal system:  Orthorhombic

Crystal class:  222 or mm2 or 2/m 2/m 2/m

Twinning: Lamellar in several directions, common

Unit cell: a = 10.62 Å, b = 9.42 Å, c = 3.92 Å

Colour:  Steel-gray

Diaphaneity:  Opaque

Luster:  Metallic

Habit:  Crystals prismatic; rod-like, elongated, striated parallel to elongation; grains

Hardness:  3 to 3.5

Specific gravity:  6.318

Cleavage:  None

Tenacity:

Streak:

Synonyms/varieties:

Comments: Found in high-grade copper ores in stratiform Pb-Zn-Cu deposits