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

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

At the Filhols Mine, Romano, Italy, ranciéite occurs in lake-deposited tuff, associated with halloysite (Dana).

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