Aurorite

Formula:  (Mn, Ag, Ca)Mn₃O₇^.3H₂O

Origin of name:  After locality; Aurora mine, Hamilton, Nevada, USA

Crystal system:  Hexagonal

Crystal class:  3 or -3

Twinning:

Unit cell: a = 7.514 Å, c = 20.734 Å

Colour:  black

Diaphaneity: Opaque, transparent on very thin edges

Luster: Metallic

Habit:  Microscopic platy or scaly grains or irregular masses

Hardness:  <3

Specific gravity: 3.81 (calculated)

Cleavage:  None

Tenacity:

Streak: Brown

Synonyms/varieties:

Comments:  Found in veinlets filling microfractures in manganoan calcite.