Images
Formula: BeFe2+2Al6O12
Multiple oxide, beryllium-bearing mineral
Specific gravity: 4.07 calculated
Hardness: 8 to 8½
Streak: White
Colour: Light green
Environments
Ferrotaaffeite-6N'3S is a very rare mineral that to date (February 2022) has been found only at the type locality.
Localities
At the type locality, the Rosendal pegmatite, Kimitoön Island, Kimitoön, Southwest Finland, the
pegmatite was quarried mainly for
K-feldspar and quartz;
tantalum-bearing minerals and beryl were
important by-products.
The pegmalite is a vertically dipping dyke in
hornblende gabbro.
Ferrotaaffeite-6N'3S occurs in the wall zone, which consists mainly of
quartz, plagioclase,
sillimanite, muscovite and
spessartine-almandine
garnet, with minor amounts of chlorite,
biotite, epidote,
allanite and
calcite
(CM.19.311-314 as pehrmanite, HOM).
The ferrotaaffeite-6N'3S occurs as small, subhedral hexagonal tabular crystals up to 25O pm across and 40 microns
thick
(Mindat).
Back to Minerals