Afwillite - Encyclopedia
Class : Silicates
Subclass : Nesosilicates
Crystal System : Monoclinic
Chemistry : Ca3(SiO3OH)2 2H2O
Rarity : Very rare
Afwillite is a rare calcium silicate, formed during the contact metamorphism of limestones. Its name comes from the initials of the general manager of the DeBeers Consolidated Mines group : Alpheus Fuller Williams (1874-1953) after its discovery in the Dutoitspan diamond mine in Kimberley (South Africa). It occurs as colorless to white striated crystals, elongated prismatic or tabular, commonly grouped in fibroradiated spherolites, and in masses. Photo © Matteo Chinellato - Domenico Preite Collection
Afwillite in the World
Afwillite in France
In France, afwillite is present in the limestones of Boisséjour, near Clermont-Ferrand (Puy-de-Dôme).
Twinning
No known twin for this mineral species.
Fakes and treatments
No known fakes or treatments.
Hardness : 3 to 4
Density : 2.63
Fracture : Conchoidal
Trace : White
TP : Translucent to transparent
RI : 1.617 to 1.634
Birefringence : 0.017
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None
Solubility : Hydrochloric and sulfuric acids
Magnetism : None
Radioactivity : None