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.

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, 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).

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, diadochite is common in some areas where altered phosphate pods are associated with sulphides. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.506).

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