Fergusonite

Formula: YNbO₄Mohs scale hardness: 5,5–6,5Specific gravity: 4,3-5,8 g/cm³Rare earth elements: Y, La, Ce, Eu, Er^{Rare earth content, %: Y}2^O3 ^{31–42; (Ce,La,..)}2^O3 ^{0.9–6; Er}2^O3 ^{0–14, REO}max^{=51,3 %}

Other constituents, %: TiO2 16–30; Nb2O5 4.3–47.4; Ta2O5 1.3–23; ThO2 1–5; UO2 0.4–12

^{Mineralklasse: Oxide}

Fergusonite is a mineral comprising a complex oxide of various rare earth elements. The chemical formula of fergusonite species is (Y,RE)NbO4, where RE = rare-earth elements in solid solution with Y. Yttrium is usually dominant (the species fergusonite-(Y)), but sometimes Ce or Nd may predominate in molar proportion (species fergusonite-(Ce) and fergusonite-(Nd)). All the other rare earth elements are present in subordinate amount, and tantalum substitutes for some of the niobium. There are Fergusonite-beta-(Nd), Fergusonite-beta-(Y), Fergusonite-beta-(Ce).

References

1. https://en.wikipedia.org

2. http://www.mindat.org/min-1480.html

3. https://books.google.cl/books?id=jPskAQAAIAAJ&pg=RA4-PA13&lpg=RA4-PA13&dq=Green+Cove+Springs+Mine+monazite&source=bl&ots=8xH_PV9MoG&sig=MkXPfqzQ6OM4zmU2OWc-eHL2-GQ&hl=ru&sa=X&ved=0ahUKEwj6-bG1mfbMAhUDE5AKHYGfCWsQ6AEIKDAD#v=onepage&q&f=false

4. https://en.wikipedia.org/wiki/Fergusonite

5. http://mrdata.usgs.gov/ree/ree.php?mineral=fergusonite