Dickinsonite-(KMnNa)

phosphate

lithiophilite

Formula: K(NaMn)CaNa3AlMn13(PO4)12(OH)2
Anhydrous phosphate containing hydroxyl, manganese mineral, arrojadite group, forms a series with arrojadite-(KFe)
Specific gravity: 3.38 to3.41
Hardness: 3½ to 4
Streak: Nearly white
Colour: Green shades to dark green, yellowish green, brownish green; green in transmitted light.
Solubility: Soluble in acids
Environments

Pegmatites

Dickinsonite is a high-temperature (about 800oC) primary mineral in granite pegmatites (HOM), commonly associated with lithiophilite (Mindat).

At the type locality, the Fillow Quarry, Branchville, Redding, Fairfield county, Connecticut, USA, dickinsonite occurs in a pegmatite associated with eosphorite, triploidite, lithiophilite, rhodochrosite, reddingite and fairfieldite (HOM, Mindat)

At Poland, Androscoggin county, Maine, USA, in some places it appears that the dickinsonite has been altered to fairfieldite; this alteration probably explains the rarity of dickinsonite. The probable sequence of formation of the minerals in the pockets is amblygonite, lithiophilite, rhodochrosite, quartz, eosphorite, reddingite, dickinsonite, fairfieldite, apatite, landesite and manganese oxide (AM15.375).

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