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Formulae:
Synchysite-(Ce): CaCe(CO3)2F
Synchysite-(Nd): CaNd(CO3)2F
Synchysite-(Y): CaY(CO3)2F
Anhydrous carbonates containing halogen, synchysite group
Specific gravity: Ce 3.9; Synchysite-(Y) 3.89 to 4.1; Synchysite-(Nd) 4.21
Hardness: Synchysite-(Ce) 4½; Synchysite-(Y) 6 to 6½; Synchysite-(Nd) 4½
Streak: Synchysite-(Ce) and synchysite-(Nd) White; Synchysite-(Y) Light brown
Colour:
Synchysite-(Ce) Grey, grey-yellow, orange-yellow, brown, beige, light green, white
Synchysite-(Y) White, reddish brown, greyish yellow, dull yellow; colourless to light yellow in transmitted light
Synchysite-Nd) Rose-pink, Pale grey-blue, light grass-green; pale violet to colourless in transmitted light
Solubility: Synchysite-(Y) and synchysite-(Ce) are readily soluble in acids
Environments:
Pegmatites
Carbonatites
Hydrothermal environments
Synchysite-(Ce) is best known from alpine fissure-type veins in granite
and alkalic syenite, where it is typically accompanied by other rare-earth minerals and
quartz, albite, the TiO2
paramorphs and
chlorite. It is found with parisite in
rare-earth-bearing pegmatites and it also occurs in carbonatites
(Webmin, HOM, MW ).
Synchysite-(Y) occurs in pegmatites, in carbonatites and in alpine fissure-type veins, where it is typically accompanied by
other rare-earth minerals and quartz, albite, the
TiO2 paramorphs and chlorite
(HOM, MW).
Localities
At the Francon quarry, Montreal, Quebec, Canada, synchysite-(Ce) is the commonest of the rare-earth minerals found in the quarry,
but still it is very rare. Associated minerals include quartz,
fluorite, dawsonite,
marcasite, pyrite,
mordenite, calcite,
celestine and baryte
(Minrec 37.1.47 ).
At the Holičky deposit, Stráž, Česká Lípa District, Liberec Region, Czech Republic, synchysite-(Nd) is an authigenic mineral
occuring as microcavity fillings in sandstone-type uranium deposits.
Associated minerals include florencite-(La),
sphalerite, manganoan siderite,
pyrite, kaolinite and
chalcedony
(HOM, Dana).
At its type locality, the Narssârssuk pegmatite, Narsaarsuk Plateau, Igaliku, Kujalleq, Greenland, Denmark, synchysite-(Ce) occurs
in a syenite pegmatite associated with
astrophyllite, catapleiite,
neptunite, epididymite,
elpidite, cordylite-(Ce),
fluorite, rhodochrosite,
polylithionite, aegirine,
microcline and albite
(HOM, Dana, Mindat).
At the Trimouns quarry, France, synchysite-(Ce) is commonly associated with allanite,
and rarely with xenotime. It may form syntaxic intergrowths with
bastnäsite
(MinRec 35.3.242).
At its type locality, the Grebnik mountain, Klina, District of Peja, Kosovo, synchysite-(Nd) occurs in
limestone at the base of the deposit
(Dana, HOM, AM 64.658).
At the Khibiny massif, Russia, synchysite-(Ce) is associated with ewaldite,
belovite-(Ce), fluorite,
nenadkevichite, ancylite-(Ce),
kukharenkoite-(Ce),
mckelveyite-(Y),
burbankite, calcite,
baryte and orthoclase
(HOM).
At Piz Blas, Val Naps, Graudunden, Switzerland, synchysite-(Ce) occurs with
gadolinite,
K-feldspar variety adularia and xenotime in
alpine veins
(Dana).
At Beddgelert Forest, Beddgelert, Gwynedd, Wales, UK, synchysite-(Y) has been found in altered
rhyolite as radiating sheaves intergrown with
quartz and K-feldspar
(MW).
At Cwmorthin Quarry, Blaenau Ffestiniog, Gwynedd, Wales, UK, synchysite-(Ce) is rare, but a small number of specimens have
been recovered from alpine fissure-type veins hosted by banded tuff -
turbidite. Associated minerals include
quartz, anatase and
xenotime
(MW).
At Gloddfa Ganol Quarry, Blaenau Ffestiniog, Gwynedd, Wales, UK, synchysite-(Ce) is very rare, occurring in alpine fissure-type
quartz veins and, with albite and
anatase, in occasional blocks of vuggy brecciated
slate; it is often sparingly coated in microscopic crystals of
pyrite
(MW).
At Manod Quarry, Blaenau Ffestiniog, Gwynedd, Wales, UK, synchysite occurs in association with
quartz and albite in alpine fissure-type veins cutting
an altered intermediate intrusive rock
(MW).
At Tanygrisiau Station, Blaenau Ffestiniog, Gwynedd, Wales, UK, synchysite-(Ce) was found as a very rare late-stage mineral in
the alpine fissure-type veins that were exposed by blasting in the mid-1970s. Associated minerals included
quartz, albite,
anatase and clinochlore
(MW).
At the Dolyhir Quarry, Old Radnor, Powys, Wales, UK, synchysite-(Ce) has been found in alpine-type fractures cutting
shale immediately below an unconformity
(MW).
At the Henry pegmatite, Cotopaxi, Colorado, USA, synchysite-(Ce) and and synchysite-(Y) are associated with
kainosite-(Y)
(Dana,AM 47.337-343).
At Quincy, Massachusetts, USA, synchysite-(Ce) occurs with parisite
(Dana).
At Dover, Morris county, New Jersey, USA, synchysite-(Y) is associated with
kainosite-(Y),
bastnäsite, xenotime,
hematite and quartz
(HOM).
At its type locality, the Scrub Oak Mine, Mine Hill Borough, Morris county, New Jersey, USA, synchysite-(Y) occurs in
aggregates mixed with xenotime, hematite and
quartz. Most of the aggregates have rims of
bastnäsite
(AM 45.92-98).
Synchysite-(Ce) also occurs at the Scrub Oak mine, intimately intergrown with quartz,
xenotime, bastnäsite and
hematite
(Dana).
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