Diadochite

phosphate

pyrite

Formula:Fe3+2(PO4)(SO4)(OH).6H2O
Compound phosphate
Specific gravity: 2.0 to 2.4
Hardness: 3 to 4
Streak: Yellow to yellow-brown
Colour: Yellow to greenish-yellow or brown, reddish brown, light green, light yellow; pale yellow to yellowish brown in transmitted light.
Solubility: Readily soluble in acids.
Environments

Pegmatites
Metamorphic environments

Diadochite is an amorphous secondary mineral in gossans and some coal deposits, formed by sulphate-rich solutions acting on earlier phosphates, possibly of post-mining origin. It also occurs in cave deposits, where the phosphate is derived from guano, and it is widespread in secondary phosphate assemblages in granite pegmatites (HOM, Mindat). Associated minerals include hydroxylapatite, delvauxite, vashegyite, pitticite, melanterite, vivianite, wavellite, leucophosphite, phosphosiderite, ferrostrunzite, beraunite, mitridatite, rockbridgeite, jahnsite, roscherite and limonite (HOM, Mindat).

At Llallagua, Bolivia, diadochite has been found in layers up to 60 cm deep (MinRec 37.2.133). At the type locality, Arnsbach, Hockeroda, Thuringia, Germany, diadochite occurs in slate altered by ground water, perhaps originally post-mine in occurrence, associated with pyrite (Mindat).

Common impurities:

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