Bursaite

Formula:  Pb₅Bi₄S₁₁

Origin of name:  Locality; Bursa Province, Turkey

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning: Frequent, with twin plane parallel {110}, lamellar

Unit cell: a = 13.399 Å, b = 20.505 Å, c = 4.117 Å

Colour:  Gray

Diaphaneity:  Opaque

Luster:  Metallic

Habit:  Small grains and prisms

Hardness: 3

Specific gravity:  7.62

Cleavage:  1; tabular, parallel to {100}

Tenacity:

Streak:

Synonyms/varieties:

Comments: May actually consist of an intergrowth of two phases, therefore classified as Q. Found in contact metamorphic scheelite deposits, in sulfide veinlets around a greisen Sn-W deposit in granite