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Formula: CaMn2+Mn2+2Fe3+2(PO4)4(OH)2.8H2O
Hydrated phosphate containing hydroxyl,
jahnsite subgroup,
jahnsite group,
manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.78 measured, 2.798 calculated
Hardness: 4
Streak: White
Colour: Brown, brownish yellow
Luminescence: Not fluorescent under UV
Environments
Localities
At the Malpensata pegmatitic dyke, Piona Peninsula, Colico, Lecco Province, Lombardy, Italy, phosphate minerals
are frequent accessory minerals occurring in masses, some of which show dendritic texture and consist mainly of
calcium-rich graftonite-(Mn). In these masses the
graftonite-(Mn) is often altered to
secondary phosphate minerals and shows a rim of
primary
ferrowyllieite crystals. The following
secondary phosphate minerals were identified:
vivianite,
metaswitzerite, jahnsite-(CaMnMn),
mitridatite,
xanthoxenite and
fairfieldite
(CM 56.645-656).
At the type locality, the Cubos-Mesquitela-Mangualde area, Mangualde, Mangualde, Viseu, Portugal,
jahnsite-(CaMnMn)
occurs as late-stage phosphate mineralisation in a granite
pegmatite, as equant, brownish yellow crystals to 0.5 mm,
associated with phosphosiderite,
zodacite, varulite and
microcline
(AM 75.401-405, Mindat).
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