Rancieite

General Information:
 Chemical Formula:
(Ca,Mn++)Mn++++4O9·3(H2O)
 Composition:
(Molecular Weight = 461.59 gm)
Calcium 6.51 % Ca
Manganese 50.58 % Mn
Hydrogen 1.31 % H 
Oxygen 41.59 % O 
 Empirical Formula:
Ca0.75Mn2+0.25Mn4+4O9·3(H2O)
 Environment:
In cavities in limonite.
 Locality:
Rancie, near Vicdessos, Ariege, France.
 Name Origin:
Named for the locality.
Physical Properties:
 Cleavage:
None
 Color:
violet brown, black, or silver gray.
 Density:
3 - 3.2, Average = 3.1
 Diaphaniety:
Transparent to Opaque
 Habits:
Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Lamellar - Thin laminae producing a lamellar structure., Stalactitic - Shaped like pendant col umns as stalactites or stalagmites (e.g.
 Hardness:
2.5-3 - Finger Nail-Calcite
 Luster:
Metallic - Dull
 Streak:
dark brown
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