Fergusonite-(Ce)
Fergusonite-(Ce) is a sulfate that is rare that is very rarely available as faceted gems. Cabochons have now been cut as curiosities as they haven’t any features which can be unique rarity. Faceted gems are extremely rare and are cut just as collector’s gems. Fergusonite-(Ce) is weakly radioactive because of its cerium (Ce) content.
The only way to obtain gemmy crystals large enough for faceting is really a discover that is recent Madagascar. These other sources produce only translucent to opaque material that is massive transparent crystals that are way too little for faceting: Chernigovskaya zone, Novopoltavskii massif, Azov Sea area, Ukraine; eastern Bayan Obo Fe–Nb–RE deposit, 130 km north of Baotou, Inner Mongolia, China; Granite Mountain, near Little Rock, Pulaski Co., Arkansas, United States Of America.
| Crystallography: | Tetragonal – Dipyramidal |
| Crystal Habit: | As prisma |
| Cleavage: | [1011] Distinct/Good |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Hardness (Mohs): | 5.5 – 6.5 |
| Density: | 5.45 – 5.48 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Weak; GRapi = 40,097.08 (Gamma Ray American Petroleum Institute Units) |
| Color: | Brownish Black to Black; if altered: Brown, Yellow or Gray |
| Transparency: | Semi-Transparent to Opaque |
| Luster: | Vitreous, Adamantine, Sub-Metallic; alters to a Dull surface |
| Refractive Index: | 2.20 – 2.30 Uniaxial ( – ); Isotropic if metamict |
| Birefringence: | 0.100 |
| Dispersion: | n/a |
| Pleochroism: | Weak |
