Fergusonite Value, Price, and Jewelry Information

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

Fergusonite

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.
Crystallography Tetragonal Crystals prismatic, pyramidal; usually masses.
Refractive Index 2.05-2.19 (mean)
Luster Vitreous; submetallic; alters to dull surface.
Hardness 5.5 - 6.5
Fracture Subconchoidal
Specific Gravity 5.6-5.8. Formanite: 7.03 (calculated)
Cleavage Traces
Stone Sizes Cabochons are cut to several inches from massive material. Faceted stones are extremely tiny (less than 1 carat).
Transparency Translucent to opaque, very rarely transparent.
Formula

YNbO4 + Er, Ce, Fe, Ti.

Pleochroism

Weak.

Optics

Isotropic due to metamictization. = 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.