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Formula: Mg5Al(AlSi3O10)(OH)8
Phyllosilicate (sheet silicate), chlorite group, forms a series
with chamosite
Ripidolite is a ferroan variety of clinochlore
Crystal System: Monoclinic
Specific gravity: 2.6 to 3.02 measured, 2.628 calculated
Hardness: 2 to 2½
Streak: Greenish white to white
Colour: Green, yellowish green, olive green, blackish green, bluish green, white, pink
Common impurities: Fe2+,Cr,Ca
Environments
Metamorphic environments
Hydrothermal environments
Clinochlore is frequently a product of contact
or low-grade regional metamorphism; it is found in
fissure veins, soils, sediments, and amygdules in volcanic rocks. Frequently associated minerals include
feldspar, quartz,
biotite, garnet,
calcite group and dolomite
group minerals, magnetite,
chromite, talc,
serpentine, chloritoid,
rutile, ilmenite,
titanite, common sulphides,
zircon and zeolites;
rarely it is found with corundum,
diaspore, margarite
or spinel. It can be a hydrothermal alteration product of a variety
of species including garnet,
biotite, pyroxene and
amphibole
(Dana, HOM).
Localities
The Two Mile and Three Mile deposits, Paddy's River, Paddys River District, Australian Capital Territory, Australia,
are skarn deposits at the contact between
granodiorite and volcanic rocks.
Clinochlore is a primary silicate that occurs in
large masses in silicate-rich areas of skarn, and as an alteration product
in the surrounding dacitic volcanics. Associated minerals include
magnetite, epidote and
clinozoisite
(AJM 22.1.34).
At Blair Duguid, near Allandale, Hunter valley, New South Wales, Australia, in a small outcrop of
andesite, clinochlore occurs rarely, associated with
earlier crystallised quartz and later
heulandite-Ca
(AJM 18.2.31).
At the Mount Kelly deposit, Gunpowder District, Queensland, Australia, the deposit has been mined for oxide and
supergene
copper ores, predominantly malachite,
azurite and chrysocolla. The ores
overlie primary zone mineralisation consisting of
quartz-dolomite-sulphide veins hosted
in dolomite-bearing siltstone
and graphitic
schist.
Clinochlore is relatively abundant as an alteration phase within some of the host siltstone, mostly replacing
detrital biotite
(AJM 22.1.17).
At Coobina, Pilbara province, Western Australia, chromium-rich clinochlore occurs in seams hosted in
ultramafic rocks. Pegmatites intruding the complex exhibit
coarse mantles of phlogopite and
chlorite at their contact with
serpentinite. Some chromium-rich clinochlore
occurs in these contact zones, on a chromite matrix and
associated with secondary
magnesite, antigorite
and traces of serpentine. It is suggested that the
clinochlore derived from the interaction of granitic fluids and the
chromite-rich ultramafic
rocks
(AJM 16.1.35-37).
At lots 10 and 11 of concession 1, Bathurst Township, Lanark County, Ontario, Canada (DeWitts corner), the deposit is
located in the Grenville Geological Province, which consists mostly of
marble, gneiss, and
quartzite.
Syenite-migmatite was
also reported in the area where the vein-dikes are located. Characteristic features of the vein-dikes include the
fact that perfectly formed euhedral crystals of different minerals can often be found floating in
calcite with no points of contact with the walls. Sometimes these crystals
have inclusions of calcite, irregular or rounded in shape. It has been argued
that at least some of the vein-dikes were formed as a result of melting of Grenville
marble.
Clinochlore is most commonly found as tiny green flakes along cracks in
spinel crystals. Occasionally, it forms flaky aggregates to 1.5 cm. In some
cases, it occurs as pseudomorphs after
spinel crystals to 2.6 cm. Most such
pseudomorphs are very crude, but in some cases the octahedral shape is
well preserved.
(R&M 97.6.556-564).
At the Alpine-type Fissures and Talc Deposit at Saint-Pierre-de-Broughton Quebec, Canada, clinochlore
occurs as aggregates to 3mm across of pseudohexagonal, platy crystals. Associated minerals include
rutile, talc and rarely
bastnäsite-(Ce)
(R&M 85.6.503).
At Yaogangxian, Yizhang county, Chenzhou, Hunan, China, clinochlore has been reported, possibly as an alteration product
of chamosite
(Minrec 42.6.578).
At Irkutsk, Russia, clinichlore occurs with magnetite
(R&M 85.4.321).
At the Witwatersrand goldfield, South Africa, clinochlore is a
secondary mineral commonly associated with fine-grained
gold. Green to green-blue clinochlore crystals to a few millimetres are
found
on secondary quartz and
calcite, either coating the crystals or as inclusions inside
quartz crystals
(R&M 96.4.322).
At the Bastnäs Mines, Riddarhyttan, Skinnskatteberg, Västmanland County, Sweden, clinochlore has been found
associated with hematite
(Minrec 35.3.195).
At Lane's Hill quarry, Stoney Stanton, Blaby, Leicestershire, England, UK, a specimen has been found that contained
well-crystallised, dark
green microcrystals of chlorite (possibly clinochlore) that occurred with three generations of Fe-bearing
dolomite and later calcite
(JRS 20.14).
In San Benito county, California, USA, crystals of clinochlore occur with
andradite
(R&M 85.4.321).
At the Hunting Hill quarry, Rockville, Montgomery county, Maryland, USA, clinochlore is found as veuns in
serpentinite, and as crystals in cavities to 1 cm in
rodingite
(Minrec 36.5.439).
At the Spurr mine, Michigame, Baraga county, Michigan, USA, clinochlore
pseudomorphs after almandine
have been found
(KL p239).
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. Clinochlore occurs with
serpentine as a massive partial alteration of
uvite/fluor-uvite crystals to 2 cm
(R&M 96.5.435).
At the Pyrites Mica mine, St Lawrence county, New York, USA, clinochlore forms as an alteration product on the surface of
some crystals of meionite, and also as an outer rind on large plates of
phlogopite
(R&M 93.4.339).
In New York City, USA, clinochlore crystals occur associated with quartz
and albite in the rock excavated for the 63rd Street subway in Manhattan.
Chrome-rich clinochlore microcrystals on serpentine have been
recovered
at an exposure on Lincoln Avenue in Staten Island
(R&M 84.3.228).
At the Tilly Foster Iron Mine, Brewster, Town of Southeast, Putnam county, New York, USA, crystals of clinochlore
with calcite and chondrodite are
known
(R&M 85.4.320).
At the Pyrites mica mine, St Lawrence county, New York, USA, clinochlore occurs as an alteration product forming
on the surface of some crystals of meionite, and also as an outer rind to 1 cm
or more on large plates of phlogopite. Some crystals of
phlogopite are nearly completely replaced by clinochlore
(R&M 93.4.339).
The type locality is Brinton's Quarry, Westtown Township, Chester county, Pennsylvania, USA.
At the Belvidere Mountain Quarries, Lowell & Eden, Orleans & Lamoille counties, Vermont, USA, clinochlore is the
major constituent of the serpentine -
chlorite contact rocks and the blackwall rock. Crystals of clinochlore
to about 4 cm occur in chlorite -
calcite - magnetite veins and in
cavities in rodingite
(R&M 90.6.529).
Alteration
tremolite, anorthite and
clinochlore to tschermakite and H2O
3☐Ca2MgSi8O22(OH)2 + 8Ca(Al2Si2O8) +
2Mg5Al(AlSi3O10)(OH)8 ⇌
5☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2 + 4H2O
(AM 76.998)
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