Images
Formula: Na(NaCa)Mg5Si8O22F2
Inosilicate (chain silicate) with double chains,
richterite root name group,
sodium-calcium amphibole subgroup,
w(OH,F,Cl)-dominant amphibole group,
amphibole supergroup
Crystal system: Monoclinic
Specific gravity: 3.174 measured, 3.213 calculated
Hardness: 5 to 6
Streak: White
Colour: Brown to brownish red, rose-red, yellow, grey-brown, pale to dark green
Solubility:
Common impurities:
Environments
Pegmatites
Carbonatites
Metamorphic environments
Hydrothermal environments
Localities
At the Earle's Farm fluoro-richterite occurrence, Monmouth Township, Highlands East Township, Haliburton County,
Ontario, Canada, crystals of fluoro-richterite to 25 cm long occur in
calcite
(R&M 94.5.413).
Fluoro-richterite from Earle's Farm - Image
At Kariåsen, Vesterøya, Sandefjord, Vestfold, Norway, two large
pegmatite veins intruded in
larvikite were exposed during blasting.
A coarse, somewhat altered pegmatite vein in the southeastern
part of the worked area contains microcline (as large crystals of
perthitic alkali feldspar up
to 30 cm long), amphibole
(“magnesio-katophorite” as large, coarse crystals up to 20 cm long), large
masses of aenigmatite (as black, shiny crystals with a typical reddish
streak), ferrokentbrooksite (as large brown to reddish brown
masses, sometimes altered to a yellowish skeleton-like or powdery material),
albite (as small crystals in cavities),
zircon (as brown to whitish crystals in cavities),
aegirine (as small, dark-green needle-shaped crystals in cavities), and
quartz (as greyish-brown crystals up to 14 mm long in cavities with
albite and epididymite).
A less-altered coarse pegmatite vein in the northeastern part
of the worked area also contains microcline,
“magnesio-katophorite”,
aenigmatite, aegirine and
albite, with the same characteristics as the other vein. Moreover, it contains
riebeckite (as pale-blue fibrous masses of acicular crystals),
annite (rare), zircon (as prismatic,
brown crystals up to 3 cm in length, often close to “magnesio-katophorite”
and aenigmatite, or as brown to yellow and whitish bipyramidal crystals up
to 1 mm in cavities with albite and
aegirine), chlorite (as globular
crystal aggregates on aegirine and
albite in cavities), pyrite (as small
crystals in cavities, occurring as cubes, octahedra, pentagonal dodecahedra, and globular crystal aggregates),
fluorapatite (as long colourless, white or yellow prismatic crystals in
cavities, often covered by pyrite crystals on the prism faces, or white
crystals up to 3 cm long in the matrix), titanite (as small, brown, striated
crystals in cavities with aegirine and
albite), and calcite (as well
developed crystals in cavities). Other minerals found in the cavities are
parisite-(Ce) (as brownish, prismatic crystals up to 5 mm long in
cavities or golden-yellow crystals covered by pyrite on the prism faces, the
basal faces being uncovered), pyrochlore (as brown octahedra up to 1 cm),
bastnäsite-(Ce) (partly as epitactic intergrowths with
parisite-(Ce) in cavities, partly as a brownish zone surrounding
fluorapatite crystals up to 2 cm in matrix),
magnetite (rare), hematite (as
rosettes of thin tabular crystals), galena (as rare cube-octahedral crystals),
molybdenite (as thin tabular crystals with a hexagonal outline up to 1 cm
in size), thorite (as brownish-black metamict masses up to 3 cm),
ilmenite (black, elongated, rounded crystals up to 14 mm long in an
alkali feldspar matrix),
epididymite (as colorless, tabular, elongated crystals up to 5 × 2 mm),
britholite-(Ce) (in reddish-brown zones surrounding
fluoroapatite),
allanite-(Ce) (as aggregates of dark reddish-brown crystals up to 1 mm),
grossular (as green crystals up to 1 mm),
andradite (as green dodecahedra up to 1 mm),
arsenopyrite (as crystal aggregates up to 0.5 mm),
bertrandite (as colorless, square tabular crystals up to 0.7 mm),
elpidite (as small pale-brown crystal aggregates, always somewhat altered),
helvine (as aggregates of numerous sub-parallel crystals up to 2 mm in a
cavity with elpidite, aegirine and
quartz), monazite-(Ce) (as small
brown crystals), zirconolite-3O (as black, prismatic crystals up to 2 mm
long in an alkali feldspar matrix) and
sphalerite (as reddish-brown crystals up to 0.6 mm).
The sodium-calcium amphiboles have been ascribed to a late stage of the
pegmatite evolution, and sodium
amphiboles (rare, but present at Kariåsen) are considered to be a
secondary hydrothermal phase
(CM 53.2.285-294).
At the type locality, Pit No. 97, Miass, Chelyabinsk Oblast, Russia, fluoro-richterite occurs as a rock-forming
component in fenites (accompanied by
microcline, albite and
phlogopite),
carbonatites and metasomatic rocks (accompanied by
calcite, dolomite,
phlogopite, magnetite,
pyrochlore, zircon,
apatite, pyrrhotite,
pyrite and ilmenite)
(AM 80.404-405).
Crystals are elongated, up to 10 cm long
(Mindat).
Fluoro-richterite from Pit No. 97 -
Image
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