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Download hereGENERAL DESCRIPTION
Ferroaxinite is a calcium and iron silicate, which is formed in metamorphic rocks and pegmatites. It is the ferrous pole of axinite (which can alos be manganesiferous and/or calcic). In contrast, axinite is more common than ferroaxinite bcause it is enriched in calcium. The crystals are brown, brown-blueish to pearly gray.
They have a vitreous lustre. Their form generally tabular and flattened crystals but it can be granular or massive. Ferroaxinite is associated to other minerals such as tourmalines, zoisites, quartz, etc.
The deposits are a few to produce world-class axinites: the Puiva deposit in Russia, the counties of Calaveras and Riverside in California, where crystals measuring up to 15 cm were found. Also in Japan, Pakistan (Ghangle), Switzerland (Grisons), Spain (Andalousia) and the UK (Cornwall).
In France, the most known localities are St. Christophe near Bourg d'Oisans (type-locality), Chamrousse in Isère; the Tarentaise and Maurienne valleys in Savoie (French Alps).
The Muséum national d’Histoire naturelle in Paris has 21 type-samples, including 6 isolated crystals, all kept within the Haüy collection.
HISTORY : Name derived from the English word "axe", because of the shape of its crystals and from "ferro" for the iron it contains
Species first described in 1909 by Waldemar Theodore Schaller (1882-1967), American mineralogist
Type-locality: Saint Christophe en Oisans, Isère, France
ANCIENT NAME : Schorl violet rhomboïdal
CHEMICAL FORMULA : Ca2 Fe2+ Al2 B Si4O15 (OH)
CRYSTAL SYSTEM : Triclinic
COLOR : Brown, dark brown
DIAPHANIETY : Transparent to translucent
LUSTER : Vitreous
STREAK : White
MORPHOLOGIE : Flattened crystals, granular, massive
HARDNESS : 6,5-7,0
CHEMICAL CLASS: 3,33
DENSITY : VIII - Silicates
GROUP : Axinite
STRUNZ CLASS BEFORE 2001 : 8/E.06-20
STRUNZ CLASS AFTER 2001 : 9.DB.20
