Fergusonite Value, Price, and Jewelry Information

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This mineral is not abundant and is known from various localities. Cabochons are cut merely as curiosities, as they have no special features that would recommend them except rarity. There are reports of transparent grains or parts of crystals that have been cut by collectors, but these are merely curiosities and are seldom encountered.

Fergusonite Information

Data	Value
Name	Fergusonite
Colors	Black, brownish black; surface altered brown, gray, or yellow.
Hardness	5.5 - 6.5
Fracture	Subconchoidal
Cleavage	Traces
Stone Sizes	Cabochons are cut to several inches from massive material. Faceted stones are extremely tiny (less than 1 carat).
Formula	YNbO₄ + Er, Ce, Fe, Ti.
Crystallography	Tetragonal Crystals prismatic, pyramidal; usually masses.
Refractive Index	2.05-2.19 (mean)
Birefringence	None. (Isotropic due to metamictization).
Pleochroism	Weak.
Optics	Isotropic due to metamictization. N = 2.05-2.19 (mean), variable.
Luster	Vitreous; submetallic; alters to dull surface.
Specific Gravity	5.6-5.8. Formanite: 7.03 (calculated)
Transparency	Translucent to opaque, very rarely transparent.

Series to Formanite YTaO₄.

Streak: Greenish gray, yellowish brown, brown.

Optics: Isotropic due to metamictization. N= 2.05-2.19 (mean), variable.

Occurrence: Granite pegmatites rich in rare earths.

California; North Carolina; Virginia; Texas: Massachusetts; Norway; USSR; Ytterby, Sweden; East Africa; Zimbabwe; Madagascar

Formanite is from Western Australia.

Comments: This mineral is not abundant and is known from various localities. Cabochons are cut merely as curiosities, as they have no special features that would recommend them except rarity. There are reports of transparent grains or parts of crystals that have been cut by collectors, but these are merely curiosities and are seldom encountered.

Name: After Robert Ferguson, a Scottish physician.