Cetineite

Formula:  (K,Na)_3-x(Sb₂O₃)₃(SbS₃)(OH)_x ^. (3+x)H₂O  (x= ~ 0.5)

Origin of name:  From locality, Cetine mine, 20 km southwest of Siena, Tuscany, Italy

Crystal system:  Hexagonal

Crystal class:  6

Twinning:

Unit cell: a = 14.251 Å, c = 5.590 Å

Colour:  Orange-red

Diaphaneity:  Transparent to translucent

Luster:  Resinous

Habit:  Tiny prismatic crystals 15µm across and 15 mm long

Hardness:  3 to 3.5

Specific gravity:  4.22

Cleavage:  1; {1000}

Tenacity: Somewhat sectile

Streak:  Orange

Synonyms/varieties:

Comments: Found in antimony deposits in highly silicified evaporites, on roasted ore after long term weathering