The results to date have indicated that the light rare earths (LREE) in the Nechalacho deposit are contained in four minerals: allanite, monazite, bastnaesite and synchisite
, and the heavy rare earths (HREE) are present in two minerals: fergusonite and zircon, the latter also being host to zirconium (Zr).
The Trimouns talc-chlorite deposit is a mineral locality of international significance, producing fine crystal specimens of rare earth element-bearing species including allanite/dissakisite, bastnasite, synchisite, parisite, hingganite and iimoriite.
Allanite/dissakisite can be associated with bastnasite, synchisite, parisite, quartz, calcite, and very rarely with hingganite.
A particularly remarkable association should be noted: it consists of millimeter-size flakes of bastnasite deposited as a crown around synchisite (a syntactic intergrowth).
Dolomite is commonly found in association with calcite and quartz, and is almost always the matrix hosting crystals of bastnasite, synchisite, and allanite and/or dissakisite.
These pseudomorphs occur as isolated crystals ranging up to 10 cm in size, and as groups of subhedral crystals associated with allanite and/or dissakisite, aeschynite, synchisite, parisite, bastnasite and, more rarely, cassiterite.
Parisite is very similar chemically to synchisite, and distinguishing them analytically is difficult (Lasmanis, 1977); however, parisite crystals characteristically taper to a point and synchisite crystals do not.
Hilaire species shortite, as well as a few loose, 5-cm prismatic sprays of synchisite
pseudomorphs after the new mineral petersenite, in an opaque, mottled white/gray-brown color.
The locality is known for samarskite and a variety of other interesting species such as fayalite, gadolinite, zinnwaldite, bastnaesite, synchisite and xenotime.
Two such are the superb synchisite in Figure 5 and the rare species tilasite [ILLUSTRATION FOR FIGURE 6 OMITTED].