Fergusonite Value, Price, and Jewelry Information

Fergusonite
By Alchemist-hp (www.pse-mendelejew.de)Alchemist-hp at de.wikipedia [CC-BY-SA-3.0-de or FAL], from Wikimedia Commons

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 Value

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Fergusonite Information

DataValue
NameFergusonite
Crystallography Tetragonal Crystals prismatic, pyramidal; usually masses.
Refractive Index 2.05-2.19 (mean)
Colors Black, brownish black; surface altered brown, gray, or yellow.
Luster Vitreous; submetallic; alters to dull surface.
Fracture Subconchoidal
Hardness 5.5 - 6.5
Specific Gravity 5.6-5.8. Formanite: 7.03 (calculated)
Cleavage Traces
Stone SizesCabochons are cut to several inches from massive material. Faceted stones are extremely tiny (less than 1 carat).
Transparency Translucent to opaque, very rarely transparent.
FormulaYNbO4 + Er, Ce, Fe, Ti.
Pleochroism Weak.
Optics Isotropic due to metamictization. N = 2.05-2.19 (mean), variable.

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.