Hydrated carbonates containing hydroxyl
Specific gravity: 3.95
Hardness: 4 to 4½
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
Plutonic igneous environments
Ancylite-(Ce) occurs in hydrothermal veins associated with felsic alkalic rocks, or in pegmatites in alkaline rocks and in carbonatites. It is an uncommon accessory mineral in some nepheline syenite.
Associated minerals include parisite-(Ce), synchysite-(Y), cordylite-(Ce), eudidymite, aegirine and microcline.
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.
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) 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, eudialite, donnayite-(Y), catapleiite, calcite, belovite-(Ce), astrophyllite, apophyllite, aegirine, kukharenkoite-(Y) and biotite (Mindat, HOM).
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