Synchysite-(Ce)

synchysite-(Ce)

epididymite

elpidite

cordylite

Images

Formula: CaCe(CO3)2F
Anhydrous carbonate, synchysite group, cerium-bearing mineral
Crystal system:
Specific gravity: 3.9
Hardness: 4½
Streak: White
Colour: Grey, grey-yellow, orange-yellow, brown, beige, light green, white
Solubility: Readily soluble in acids
Environments:

Plutonic igneous environments
Pegmatites
Carbonatites

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).

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 ).
Synchysite-(Ce) from the Francon Quarry - Image

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).
Synchysite-(Ce) from the Trimouns Quarry - Image

At the Monte Cervandone area, Devero Alp, Baceno, Verbano-Cusio-Ossola Province, Piedmont, Italy, synchysite-(Ce) is fairly common, especially in clefts on the slopes of Monte Cervandone; good finds have also been made around the Gischihorn and Helsenhorn. Unaltered synchysite-(Ce) crystals up to 1 cm are yellow to orange, medium brown and red-brown; they are pseudohexagonal and barrel-shaped, with stepped sides and strong cleavage. Pseudomorphs and partial pseudomorphs of gasparite-(Ce) after synchysite-(Ce) are also known (MinRec 56.3.318).
Synchysite-(Ce) from the Monte Cervandone area - Image

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).
Synchysite-(Ce) from the Khibiny Massif - Image

At Piz Blas, Val Naps, Graudunden, Switzerland, synchysite-(Ce) occurs with gadolinite, K-feldspar variety adularia and xenotime in alpine veins (Dana).

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).
Synchysite-(Ce) from the Cwmorthin Quarry - Image

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).
Synchysite-(Ce) from the Gloddfa Ganol Quarry - Image

At Manod Quarry, Blaenau Ffestiniog, Gwynedd, Wales, UK, synchysite-(Ce) occurs in association with quartz and albite in alpine fissure-type veins cutting an altered intermediate intrusive rock (MW).
Synchysite-(Ce) from the Manod Quarry - Image

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).
Synshysite-(Ce) from the Dolyhir Quarry - Image

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).
Synchysite-(Ce) from Quincy - Image

The Scrub Oak Mine, Mine Hill Borough, Morris county, New Jersey, USA, synchysite-(Ce) occurs intimately intergrown with quartz, xenotime, bastnäsite and hematite (Dana).

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