Axinite-(Fe)

minerals

sorosilicate

boron mineral

Formula: Ca4Fe2+2Al4[B2Si8O30](OH)2
Sorosilicate (Si2O7 groups), axinite group
Specific gravity: 3.23 to 3.32
Hardness: 6½ to 7
Streak: White
Colour: Brown, clove-brown, plum blue, pearl grey
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Environments:

Plutonic igneous environments
Pegmatites rarely
Metamorphic environments
Hydrothermal environments

Axinite-(Fe) is found in quartz - calcite veins, in alpine-type veins, as shear zone mineralisation, especially in high grade metamorphic zones, as hydrothermal metasomatism of granite or aplite, rarely in granite pegmatites, and in the contact zones surrounding granite intrusions (Dana).
Associated minerals include epidote - clinozoisite, grossular, vesuvianite, ilvaite, hedenbergite, hastingsite, andradite, zoisite, actinolite, datolite, tourmaline, calcite, albite, quartz, danburite, prehnite, titanite, plagioclase, microcline, arsenopyrite, pyrite and zeolites (Dana, HOM).
Rarely, axinite-(Fe) may be replaced by clinochlore - chamosite or clay minerals (Dana).

The type localities is Saint Christophe-en-Oisans, Isère, Auvergne-Rhône-Alpes, France.

At the Belvidere Mountain Asbestos Quarries, Lowell/Eden, Vermont, USA, a specimen has been found with crystals of axinite-(Fe) to 2 cm associated with epidote and chrysotile (R&M 90.6.527).

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