Aenigmatite - Encyclopedia
Class : Silicates
Subclass : Inosilicates
Crystal System : Triclinic
Chemistry : Na2Fe5TiSi6O20
Rarity : Rare
Aenigmatite is an infrequent mineral of silica-deficient alkaline igneous rocks. Its name comes from the Greek aenigma (enigma) and reveals the problem initially posed by its chemical composition. It is a velvety black mineral that forms rather coarse elongated prismatic crystals, measuring up to 8 cm, and xenomorphic masses. It is not used in any particular field and remains little known to collectors.
Main photo : Aenigmatite from Água de Pau Volcano, São Miguel, Azores, Portugal © Luigi Chiappino© Luigi Chiappino
Aenigmatite in the World
Aenigmatite in France
Aenigmatite is reported in France in Velay (Haute-Loire) as well as in Rapa Island (French Polynesia).
Twinning
The aenigmatite twins by rotation on (011) or about [010].
Fakes and treatments
No known fakes or treatments.
Hardness : 5.5 to 6
Density : 3
Fracture : Irregular
Trace : Red-brown
TP : Translucent to opaque
RI : 1.780 to 1.900
Birefringence : 0.009 to 0.010
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None
Solubility : Hydrofluoric acid
Magnetism : Paramagnetic
Radioactivity : None