Aeschynite

Aeschynite (or priorite)

Formula: (Y,Er,Ca,Th)(Ti,Nb)₂O₆

Mohs scale hardness: 5-6

Specific gravity: 4,5-4,9 g/cm³

^{Rare earth elements (REE): Eu, Nd, Pr, Y, Sm, Ce, Er}

^{Rare earth content, %: Ce}2^O3 ^{15.5–19.5 (3.7–4.3); (Y,Er)}2^O3 ^{21.1–28.7 (0.9–4.5); REO}max^{=32,4 %}

^{Other constituents, %: TiO}2 ^{21.2–24 (21.8–34); Nb}2^O5 ^{23.8–32.5 (15–36.7); Ta}2^O5 ^{0–7 (0–1.3); ThO}2 ^{11.2–17.5 (0.6–7.9); UO}2 ^{0.5–3; CaO 2.3–2.7 (1–4.1); FeO 2.2–4.3 (1.4–5.6); SnO}2 ^{0–0.3; PbO 0.08; MnO 0–2 Mg.}

^{Mineralklasse: Oxide}

^{Uses: A very minor ore of rare earth elements and as mineral specimens.}

^{Rare Earth Oxides such as aeschynite form from the leftover elements that other minerals seem to not want. Other rare earth oxides such as fergusonite, samarskite and euxenite have very similar properties to aeschynite and are often associated with each other, compounding the problem. Even the common oxide, rutile, is almost indistinguishable from these rare earth oxides without chemical tests when rutile is found massive.}

^{Associated Minerals include quartz, feldspars, euxenite, fergusonite, monazite, columbite, tantalite, allanite, gadolinite, xenotime and zircon.}

^{Notable Occurrences include the Ural Mountains of Russia; Urstad, Hittero, Norway and Madagascar.}

^{Best Field Indicators are luster, fracture, color, streak, associations, environment and specific gravity.}

References

1. https://en.wikipedia.org

2. http://www.mindat.org/min-39.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. http://www.galleries.com/Aeschynite