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Formula: Mg9(SiO4)4F2
Nesosilicate (insular SiO4 groups), humite subgroup,
humite group
Crystal System: Monoclinic
Specific gravity: 3.17 to 3.35 measured, 3.279 calculated
Hardness: 6
Streak: White
Colour: Brown, yellow, white, orange, reddish brown.
Common impurities: Fe,Ti,Al,Mn,Ca,(OH)
Environments:
Carbonatites
Metamorphic environments
Clinohumite may be found in
dolostone,
kimberlite,
limestone and
peridotite.
Titanium is a minor constituent of clinohumite in most occurrences.
Clinohumite is stable throughout the
upper mantle to depths of at least 410 km.
It occurs in contact metamorphic zones in
dolostone and metasomatised limestone
adjacent to felsic plutonic rocks, in serpentine and
talc schist, and also in carbonatites.
Associated minerals include grossular,
wollastonite, forsterite,
monticellite, cuspidine,
fluoborite, ludwigite,
dolomite, calcite,
talc, biotite,
spinel, vesuvianite,
sanidine, meionite and
nepheline
(HOM).
Localities
Amity, Town of Warwick, Orange county, New York, USA, is an area of
granite intrusions into
marble and associated
gneiss. The marble is
mostly composed of white crystalline calcite that often has small flakes
or spheres of graphite and
phlogopite. Clinohumite occurs as crude brownish yellow crystals
in the marble, almost always associated with
spinel
(R&M 96.5.435-436).
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