DIADOCHITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated phosphates
    Crystal system : Triclinic
    Chemistry : Fe2(PO4)(SO4)(OH) 5H2O
    Rarity : Common


Diadochite (formerly called destinezite) is a complex hydrated phosphate which admits in its structure a certain number of SO4 groups to replace PO4 groups. It is a secondary mineral formed by degradation of primary phosphates, hence its name which comes from the Greek diadokhos (successor). It is found in varied environments : gossans, coal deposits, granite pegmatites but also, more anecdotally, on guano crusts in caves. Diadochite is a recently formed phosphate which sometimes appears in mine galleries. It accompanies a sometimes large procession of primary and secondary phosphates, and sulfates. Diadochite is rarely crystallized in six-sided lamellar microcrystals, more commonly in reniform, botryoidal or stalactitic aggregates, sometimes collomorphic. A mineral of sometimes current formation, its atoms have not always had time to organize themselves and diadochite is also commonly amorphous, in earthy or glassy masses. Its color is in different tones of brown, red-brown, yellow and orange, sometimes greenish-yellow.

Main photo : Diadochite from Old strip mine, Jackson Township, Coshocton County, Ohio, USA © Chris Emproto

Diadochite in the World

Occurrences of diadochite are quite numerous but sites with aesthetic samples are rare. Litosice (Czech Republic) is known for its large nipple masses ; other Bohemian sites also yielded comparable samples. In the United States, the Tip-Top pegmatite (South Dakota) and the New Idria mine (California) provided interesting samples, as well as the Jackson coal mine (Ohio). In Europe, diadochite is particularly known in Germany, in the Saalfeld region (Turkey) and in several Belgian localities (Visé, Védrin, etc...).

Photo on the right : Diadochite from the Clara Mine, Germany © Michael Förch


Diadochite in France

In France, diadochite is present in Peychagnard (Isère) as well as in Poullaouen (Finistère).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.



Hardness : 3 to 4
Density : 2.0 to 2.4
Fracture : Conchoidal to sub-conchoidal
Streak : Yellow to yellow-brown


TP : Transparent to opaque
RI : 1,600 to 1,670
Birefringence : 0.050 to 0.055
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None


Solubility : Acids


Magnetism : None
Radioactivity : None