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Formulae:
Ancylite-(Ce): CeSr(CO3)2(OH).H2O
Ancylite-(La): LaSr(CO3)2(OH).H2O
Hydrated carbonates containing hydroxyl, ancylite group
Specific gravity: 3.95
Hardness: 4 to 4½
Streak: White
Colour: Light yellow, orange-yellow, yellow-brown, grey. Ancylite-(Ce):Colourless in transmitted light.
Ancylite-(La):colourless to pale yellow in thin section.
Solubility: Readily soluble in acids
Environments:
Plutonic igneous environments
Pegmatites
Carbonatites
Hydrothermal environments
Ancylite-(Ce)
Ancylite-(Ce) occurs in hydrothermal veins associated with felsic alkalic rocks, or in pegmatites in alkaline rocks and
in carbonatites
(Dana).
It is an uncommon accessory mineral in some nepheline syenite
(HOM).
Associated minerals include parisite-(Ce),
synchysite-(Y), cordylite-(Ce),
eudidymite, aegirine and
microcline
(HOM).
At Mont Saint-Hilaire, Quebec, Canada, ancylite occurs in the carbonatite
(Dana).
At the type locality, Narsaarsuk pegmatite, Greenland, Denmark, ancylite-(Ce) occurs in druses in pegmatite veinlets
in nepheline syenite associated with
aegirine, albite,
microcline, zircon,
synchysite-(Y), cordylite-(Ce)
and eudidymite
(Dana, Mindat).
At Cripple Creek, Colorado, USA, microscopic particles of ancylite-(Ce) have been found in
phonolite syenite.
(MinRec 36.2.162)
In the Bearpaw mountains, Montana, USA, ancylite-(Ce) occurs in veins intergrown with
calcite, quartz and
baryte
(Dana).
In New York city, USA, ancylite-(Ce) and calcioancylite-(Ce)
crystals have been found an old specimen of stilbite crystals that was
collected at College Point, Queens, New York City in rock that was dumped there from the excavation
of the 63rd Street subway tunnel
(R&M 84-3.225).
Ancylite-(La)
Ancylite-(La) occurs in hydrothermal veins in nepheline syenite
(Webmin, HOM).
At the type locality, Marchenko Peak, Murmanskaya Oblast, Russia, ancylite-(La) is a rare mineral in
nepheline syenite associated with
nenadkevichite, loparite-(Ce),
fluorapatite, eudialyte,
donnayite-(Y), catapleiite,
calcite, belovite-(Ce),
astrophyllite, apophyllite,
aegirine, kukharenkoite-(Y)
and biotite
(Mindat, HOM).
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