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Fergusonite-(Y) - Sold


The mineral name fergusonite-(Y) honors Sir Robert Ferguson (1767-1840), landowner, politician, and mineral collector in Scotland (Haidinger, 1825). Ferguson's collection remained intact until 1997, when Brian Lloyd purchased the collection.

Fergusonite-(Y) is nominally a yttrium niobium oxide, but samples typically contain tantalum, other rare earth elements and uranium. In fergusonite-(Y), a minor uranium content causes damage to the atomic arrangement of fergusonite-(Y), leading to a loss of crystallinity. The mineral becomes amorphous in a process known as metamictization. Recognition of fergusonite-(Y) therefore depends on combining chemical analysis with study of its external crystal form.

This is a long prismatic crystal, showing crude crystal form. The terminations appear to be very rough pinacoids on a twisted tetragonal prism. The mineral shows superficial brown alteration, itself being resinous black on a fresh surface. There is a bit of adhering clay.