Ranciéite

oxide

halloysite

Formula: (Ca,Mn2+)0.2(Mn4+,Mn3+)O2.0.6H2O multiple oxide
Specific gravity: 3.2
Hardness: 2½ to 3
Streak: Dark brown
Colour: Black, brownish, violet
Environments:

Sedimentary environments

Localities

France

At the type locality, Rancié, Occitanie, ranciéite occurs in cavities in limonite.

Italy

At the Filhols Mine, Romano, it occurs in lake-deposited tuffs, associated with halloysite.

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