Adelite - Encyclopedia

    Class : Phosphates, arsenates, vanadates
    Subclass : Anhydrous arsenates
    Crystal System : Orthorhombic
    Chemistry : CaMg(AsO4)(OH)
    Rarity : Very rare

Adelite is an extremely rare arsenate of some metamorphic manganese-iron or zinc deposits. Its name comes from the Greek adelos (dark) which emphasizes its lack of transparency. It forms small elongated or tabular crystals, and small hemispherical masses, colorless, or of various colors (gray-yellowish to yellow, gray-bluish to gray, pale green, brown...). Photo © Ulf Nyberg.

Adelite in the World

The metamorphic manganese deposit of Långban (Sweden) gave beautiful small tabular crystals of 5 mm which are the best known representatives of the species, associated with braunite and hausmannite. Adelite is also present in particular in the metamorphic zinc deposits of Franklin and Sterling Hill (New Jersey, USA).

Adelite in France

Adelite is not present in the French subsoil.


No twin known for the species.

Fakes and treatments

No known fakes or treatments.

Hardness : 5
Density : 3.71 to 3.76
Fracture : Conchoidal to uneven
Trace : White

TP : Translucent to transparent
RI : 1.712 to 1.731
Birefringence : 0,019
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None

Solubility : Hydrochloric and nitric acids

Magnetism : None
Radioactivity : None