Andorite

Formula:  PbAgSb₃S₆

Origin of name:  For Andor von Semsey (1833-1923), Hungarian nobleman, who was also an amateur mineralogist

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:  on {110}

Unit cell:   a = 13.01 Å, b = 19.19 Å, c = 4.27 Å

Colour:  Dark steel-gray

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Crystals stout prismatic, striated parallel to elongation; thick to thin tabular; commonly massive

Hardness:  3 to 3.5

Specific gravity:  5.35 to 5.38

Cleavage:  None

Tenacity:  Brittle

Streak:  Black

Synonyms/varieties:  Quatrandorite

Comments: Of hydrothermal origin