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Formula: NaCa
Inosilicate (chain silicate), pargasite group,
amphibole supergroup
Crystal System: Monoclinic
Specific gravity: 3.18 measured, 3.19 calculated
Hardness: 6
Streak: Grey to greenish grey
Colour: Black
Luminescence: No fluorescence under UV
Environments
Fluoro-pargasite is a relatively new mineral,approved in 2003. It occurs in
granulite facies metacarbonate rocks, associated with
calcite, actinolite,
titanite, phlogopite and
diopside
(HOM).
Localities
At the type locality, Edenville, Town of Warwick, Orange county, New York, USA, fluoro-pargasite occurs in the
Franklin Marble, a late Precambrian metacarbonate sequence outcropping
in New Jersey and New York State. The metamorphic grade is probably upper
amphibolite to
granulite facies. The peak conditions of metamorphism
for the Franklin Marble, in the area where the holotype material is
reported to have come from, have been estimated to be 836 ± 40°C and 4 to 7 kbar. The holotype specimen consists of
a 13 x 7 x 4.5 cm3 stubby black prismatic crystal associated with
calcite, actinolite, and
titanite, with phlogopite on
its cleavage and crystal faces.
Specimens from Edenville in the Seaman Museum collection are similar, but with
titanite and diopside as the only
associated species
(CM 43.1423-1428).
A specimen from Russell, St. Lawrence county, New York, USA, is from another sequence of Precambrian carbonates
characterised by similar peak conditions of metamorphism
(CM 43.1423-1428).
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