Cyrilovite - Encyclopedia

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated phosphates
    Crystal system : Tetragonal
    Chemistry : NaFe3(PO4)2(OH)4 2H2O
    Rarity : Rare

Cyrilovite (formerly called avelinoite) is a hydrated iron and sodium phosphate. It is a rare secondary mineral of granitic phosphate pegmatites and iron deposits which associates with other primary and secondary phosphates. It owes its name to its locality of discovery : Cyrilov (Czech Republic). It usually forms crusts and botryoidal to radiate aggregates, more rarely small thick tabular crystals (less than 1 mm) or octahedra. Cyrilovite is yellow to yellow-brown and brown in color.

Main photo : Cyrilovite from Eduardo Claim, Minas Gerais, Brazil © Gianfranco Ciccolini

Cyrilovite from Echassières, Allier, France © Michael Förch
Cyrilovite from Villefranche-de-Rouergue, Aveyron, France © Jean-Marc Johannet
Cyrilovite from Commanderie, Deux-Sèvres, France © Yannick Vessely
Cyrilovite from Echassières, Allier, France © Pascal Chollet

Cyrilovite in the World

Although rare, cyrilovite is nonetheless quite widely distributed but always in very limited quantities. It is thus known in the classic American pegmatites of New Hampshire and South Dakota, in the Portuguese pegmatites of Sabugal and Mangualde, in the Brazilian pegmatites of Galiléia (Minas Gerais), as well as in those of Hagendorf (Bavaria, Germany). Cyrilovite is also present in the oxidation zone of the immense phosphate iron deposit of Iron Monarch (Australia).

Cyrilovite in France

In France, cyrilovite is reported in the ancient oolitic iron deposit of Pluherlin, near Rochefort-en-Terre (Morbihan), it is also found in Echassières (Allier), at the Commanderie Mine (Deux-Sèvres), in St-Yrieix-la-Perche (Haute-Vienne) and in Villefranche-de-Rouergue (Aveyron).

Twinning

No known twin for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 4
Density : 3.08 to 3.09
Fracture : Conchoidal
Streak : Yellow

TP : Translucent to transparent
RI : 1.769 to 1.805
Birefringence : 0.033
Optical character : Uniaxial -
Pleochroism : Weak
Fluorescence : None

Solubility : -


Magnetism : None
Radioactivity : None

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