Neotocite

phyllosilicate

rhodonite

Formula: (Mn,Fe)SiO3.H2O(?) phyllosilicate (sheet silicate)
Forms a series with hisingerite
Specific gravity: 2.43
Hardness: 3 to 4
Streak: Brown
Colour: Black, dark brown to dark olive-green, dark red-brown
Solubility: Decomposed by hydrochloric acid (Dana)
Environments:

Pegmatites
Hydrothermal environments

Neotocite is a secondary mineral formed from the alteration of rhodonite and other manganese silicates, associated with rhodonite, calcite and quartz. It is frequently found as veins in weathered manganese-bearing pyroxenes, especially rhodonite, and also in spessartine. It is also found lining fractures in granite pegmatites (Dana).

Common impurities: Al,Mg,Ca,Na,K,C

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