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.
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,
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).
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