Marsturite

marsturite

rhodonite

willemite

axinite-(Mn)

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Formula: NaCaMn2+3Si5O14(OH)
Inosilicate (chain silicate), manganese-bearing mineral
Crystal System: Triclinic
Specific gravity: 3.46 measured, 3.465 calculated
Hardness: 6
Streak: White
Colour: Light pink to white
Common impurities: Fe,Mg
Environments

Metamorphic environments

Localities

At the Tanohata mine, Tanohata, Shimohei District, Iwate Prefecture, Japan, marsturite is associated with natronambulite and mangano-ferri-eckermannite (HOM).

At the type locality, the Franklin Mine, Franklin, Franklin Mining District, Sussex county, New Jersey, USA, marsturite occurs as crystals up to 0.5 mm in size, implanted for the most part on abundant yellow axinite-(Mn) and and epitaxially overgrown on rhodonite, with willemite. The sequence of formation is axinite-(Mn) containing euhedral colourless willemite, followed by rhodonite, followed by marsturite, hence marsturite is found coating willemite, rhodonite and axinite-(Mn) and is the last mineral to form (AM 63.1187-1189). The marsturite occurs as a secondary mineral in cavities in fractures traversing massive franklinite-willemite-zincite ore in a metamorphosed zinc-manganese-iron orebody hosted in the Franklin marble. Associated minerals include ganophyllite and franklinite, as well as rhodonite, axinite-(Mn) and willemite (Mindat, HOM).

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