Description
Fergusonite-Y has a hardness of between 5½ – 6½, and a specific gravity of around 5.7, and was named after Robert Ferguson, a Scottish landowner, politician and mineral collector.
Wikipedia says that some Yttrium-dominant minerals such as Fergusonite may contain as much as 7% dysprosium, and that no dysprosium-dominant mineral is known to exist as dysprosium is “never encountered as a free element”, so this may be the closest anyone can come to collecting Dysprosium as it presents itself in nature!
Mindat has a specimen that was sampled and shown to contain: 45.2% Nb₂O₅, 28.46% Y₂O₃, 5.09% UO₂, 4.44% Ta₂O₅, 3.79% Yb₂O₃, 3.09% Dy₂O₃, 1.76% Gd₂O₃, 1.58 % CaO, 1.39 & Sm₂O₃, 1.04% Er₂O₃, 1.01% Lu₂O₃, 0.51% Nd₂O₃, and 0.31% ThO₂, with 7% accounting for other unrelated molecules.
Whether this specific specimen contains any additional Rare Earths besides Yttrium, this rock would still make for a great sample for element collectors, as well as for those collecting the rare rocks from Colorado!
Fergusonite-Y is known to occur in roughly a couple hundred localities around the world on most continents and in six Colorado counties, mostly near pegmatites, so no matter where you happen to be, keep an eye out for this valuable rock on your next hike!
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