What is Fergusonite-(Y)?
Fergusonite-(Y) is a yttrium niobium oxide of rare-element pegmatites, usually brown to black and often compositionally substituted.
Mineralogy and structure
Reference formula: YNbO4. Fergusonite-(Y) has the ideal formula YNbO4 and polymorphs with different symmetry. The selected COD model is the natural monoclinic form, not the high-temperature tetragonal polymorph.
Colour and appearance
Typical colours include brown, black, yellow-brown. The usual prismatic, granular, massive habit and resinous, sub-metallic lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Fergusonite-(Y) forms in or is associated with rare-element granitic pegmatites, alkaline rocks and heavy-mineral assemblages. Important documented localities include Norway, Sweden, Brazil, Madagascar, Canada, Russia and the United States.
Collecting and care
Keep labelled and avoid cutting or grinding; unusual rare-earth and uranium-bearing samples may require specialist handling.
Fergusonite-(Y) and rare-element pegmatites
Fergusonite-(Y) is a good example of how a dark, modest-looking mineral can reveal a highly evolved pegmatite and the concentration of rare elements. Collecting symbolism around hidden value is metaphorical and should not be confused with a physical effect.
Traditional associations
Fergusonite-(Y) has no stable birthstone or zodiac tradition. Any assignment belongs to modern folklore and may differ from one source to another.
