Ardennite - Encyclopedia
Class : Silicates
Subclass : Sorosilicates
Crystal System : Orthorhombic
Chemistry : Mn4(Al,Mg)6(SiO4)2(Si3O10)[(As,V)O4](OH)6
Rarity : Rare
Ardennite is a complex silicate of manganese and aluminum which also includes arsenate and vanadate groups, it is found in hydrothermal veins and pegmatites as well as in the oxidation zone of manganese deposits. It owes its name to its locality of discovery : Ottré, near Salmchâteau in the Belgian Ardennes. The crystals, prismatic to acicular lamellae are rare and often united in rosettes, in fibroradiated groups, measuring up to 4 cm, or in crystalline aggregates. Its color is usually orange-yellow to orange-brown, sometimes black-brown to black, with an adamantine luster.
Main photo : Ardennite of Vielsalm, Belgium - © Jan Vanheuverzwijn
Ardennite in the World
Right picture : Ardennite of Salmchâteau, Belgium - © Andrew Hodgson
Twinning
No known twins for this mineral species.
Fakes and treatments
No fake identified for this mineral species.
Hardness : 6-7
Density : 3.7
Fracture : Irregular to sub-conchoidal
Trace : White
TP : Opaque to transparent
RI : 1.740 to 1.780
Birefringence : 0.015 to 0.020
Optical character : Biaxial +
Pleochroism : Strong
Fluorescence : None
Solubility : -
Magnetism : None
Radioactivity : None