Rhabdophane-(Ce) , Fluorcalciopyrochlore , Albite , Aegirine , Lorenzenite Field of view: 6.3 x 4.6 mm Locality: Poudrette quarry (De-Mix quarry; Demix quarry; Uni-Mix quarry; Carrière Mont Saint-Hilaire; MSH), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada Description: Found Nov 2001. “Fuzzy” orange fluorcalciopyrochlore on black aegirine with partly transparent pink albite (to 3.7 mm). The small tan needles on aegirine which can be seen in the gap between the two main albite crystals are lorenzenite, some apparently epitactic. (The lorenzenite has been verified via EDS. See [1] for a better example and an EDS scan.) The pyrochlore is clearly “fuzzy” because it is encrusted by more pyrochlore of similar compositio. There are a very few "naked" crystals (not on this specimen) that also appear to be yellowish. However, some of the crust can be removed with HCl, suggesting that it is cemented by calcite. Update April 2017: Quick and dirty EDS of uncoated samples on matrix seemed to show very high Ta for both the "crust" and the "naked" crystals (after removal of crust). For the "naked" crystals, peak heights for Ta > Nb were oberved, which would suggest "microlite group". However, consultation with a mineralogist very familiar with "pyrochlore" at MSH, strongly suggests that the "Ta" peaks are really "Si", and that this is just "pyrochlore" with lots of Si. According to the expert, high levels of Si have been found repeatedly in MSH pyrochlores. It is not know if this is because the pyrochlore is metamict or because Si has actually been incorporated into the pyrochlore structure (as has been suggested by some.) See the Analysis "photos" Feb 2018: The two "pyrochlore" species now confirmed at MSH are fluornatropyrochlore and fluorcalciopyrochlore, assuming that this too is a "fluor-pyrochlore" (EDS can't tell), it seems more likely that it is fluorcalciopyrochlore than fluornatropyrochlore. However, Na is detected with difficulty and its seeming near absence in the scans could be misleading. Nonetheless, I have tentatively changed the caption from "pyrochlore group" to "fluorcalciopyrochlore". Associated with abundant rhabdophane-(Ce) and acicular epididymite (both analyzed) with “bitumen” in a very dirty pegmatite. See the "related" (same minID) photos. — Photo: Modris Baum · Public domain
Fluorcalciopyrochlore
Fluorcalciopyrochlore is an IMA-recognized mineral species in the halide class, with the chemical formula (Ca,Na)₂(Nb,Ti)₂O₆F.
It crystallizes in the cubic crystal system (space group Fd-3m). It is a member of the Pyrochlore-Pyrochlore structural group.
Key properties: Mohs hardness 5; specific gravity 4.34; Light yellow streak; Adamantine to greasy luster.
IMA symbol Fcpcl, IMA status: approved, named in 2013.
Found in the dolomitic carbonatite.
It is found associated with Dolomite, calcite, aegirine, riebeckite, diopside, fluorite, barite, phlogopite, rutile, britholite-(Ce), bastnäsite-(Ce), zircon, magnetite, pyrite, fersmite.
The name refers to a member of the pyrochlore group with prefixes to indicate dominant fluorine (fluor) in the Y site and dominant calcium (calcio) in the A site.