Hydroxide, brucite group
Specific gravity: 3.25
Colour: Colourless, greenish, bluish (fresh), brown to black (exposed); flesh-red or amethystine in transmitted light
Solubility: Easily soluble in dilute hydrochloric acid
Common impurities: Mg
Igneous volcanic environments
Pyrochroite is a primary manganese mineral occurring in
some volcanogenic massive
sulphide deposits, and also a hydration product of manganosite, in turn
metamorphosed from rhodochrosite (HOM), or a
secondary mineral after
Associated minerals include hausmannite, rhodochrosite, manganosite, galaxite, tephroite, alabandite, lead, baryte, calcite and dolomite (HOM).
At Franklin and Sterling hill, New Jersey, USA, pyrochroite occurs in secondary hydrothermal veinlets cutting franklinite ore, with rhodochrosite, calcite, willemite, gageite, chlorophoenicite and hodgkinsonite (Dana).
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