Ferrocarpholite

Formula: Fe²⁺Al₂Si₂O₆(OH)₄
Inosilicate (chain silicate), carpholite group, forms a series with carpholite and with magnesiocarpholite
Crystal System: Orthorhombic
Specific gravity: 3.04 measured, 3.05 calculated
Hardness: 5½
Streak: Greenish white
Colour: Grey-green, dark green
Common impurities: Ti,Mn
Environments

Metamorphic environments

Ferrocarpholite occurs in quartz veins in blueschists of low metamorphic grade, formed from felsic tuffs at about 250^oC and 3 kbar. Associated minerals include quartz, aragonite, glaucophane, lawsonite, pumpellyite, jadeite, muscovite variety sericite and stilpnomelane (HOM, Mindat, Webmin).

Localities

At Haute-Ubaye, Alpes-de-Haute-Provence, Provence-Alpes-Côte d'Azur, France, ferrocarpholite is found in blueschist with minerals including quartz, glaucophane, lawsonite and jadeite (Dana).

There are three co-type localities, Peleroe, Tamondjengi and Tomata, all in Southeast Sulawesi Province, Indonesia. Here ferrocarpholite occurs in schistose carpholite-quartzite, associated with zircon, tourmaline, muscovite variety sericite, rutile, quartz, hematite, chlorite group minerals and biotite (AM 36.736-745, Mindat).
Glaucophane requires considerable pressure for its formation, as does lawsonite. It could not be definitely determined whether the ferrocarpholite was produced during metamorphism in this facies, or during slightly younger or older metamorphism, but it is most probably a product of metamorphism in the glaucophane-schist facies (AM 56.1976-1982).

In Calabria, southern Italy, ferrocarpholite occurs in quartz-bearing veins in an area also containing rocks with glaucophane, lawsonite, pumpellyite, aragonite and jadeite, associated with quartz. It appears that the ferrocarpholite has been produced in part by metamorphismin the glaucophane-schist facies and in part by a metamorphism of a lawsonite-albite facies (AM 56.1976-1982).

At the Pollino Massif, southern Italy, ferrocarpholite occurs in veins and coexists with quartz, calcite, chlorite and muscovite variety phengite. In particular, the tiny ferrocarpholite crystals are closely associated with quartz, suggesting simultaneous formation (AM 106.123-134).

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