Coffinite
Coffinite is an extremely radioactive mineral that is silicate is a member of the Zircon band of minerals that includes Coffinite, Hafnon, Thorite, Thorogummite and Zircon. It is extremely uncommon and primarily for collectors of rare and unusual gems, black gems or gems that are radioactive. Coffinite contains over 72% uranium and surpasses Autunite, Thorianite and Thorite in radioactivity. It will be stored away from other minerals and gems that may be damaged by radioactivity. Human exposure and contact to Coffinite mineral specimens or gems should be limited!
There are numerous minor occurrences of Coffinite; those mentioned are for studied or well-crystallized material. In America, within the La Sal No. 2 mine, Beaver Mesa, Gateway district, Mesa County, as well as in the Peanut mine, Montrose County, Colorado; Mount Pisgah San Bernardino County, California; around the Jackpile and Crownpoint mines, Valencia County, New Mexico; in the Mi Vida, Homestake, along with other mines, San Juan County, Utah. From Wölsendorf, Bavaria; at Niederramstadt, near Schneeberg, Johanngeorgenstadt, and Niederpfannenstiel, Saxony, Germany. At Hüttenberg, Carinthia, Austria. From Jáchymov (Joachimsthal) and Pribram, Czech Republic. In the Geevor mine, St. Just, the South Terras mine, St. Stephen-in-Brannel, and the Roskrow United mine, Ponsansooth, Cornwall, England.
| Category: | Nesosilicate |
| Chemical Formula: | U(SiO4)1-x(OH)4x |
| Uranium Silicate Hydroxide | |
| Molecular Weight: | 327.71 gm |
| Composition: | Uranium | 72.63 % | U | 82.40 % | UO2 |
| Silicon | 7.71 % | Si | 16.50 % | SiO2 | |
| Hydrogen | 0.12 % | H | 1.10 % | H2O | |
| Oxygen | 19.53 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Tetragonal – Ditetragonal Dipyramidal |
| Crystal Habit: | As crystals, rarely > 20 µm, and in colloform to botryoidal incrustations, radially fibrous. Commonly pulverulent, in aggregates of extremely fine crystallites, or massive. |
| Twinning: | None |
| Cleavage: | None |
| Fracture: | Irregular to Sub-Conchoidal |
| Tenacity: | Brittle or Friable |
| Moh’s Hardness: | 5.0 – 6.0 |
| Density: | 5.10 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Very Strong; GRapi = 5,176,587.32 (Gamma Ray American Petroleum Institute Units) |
| Health Warning: | Contains uranium – always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. Avoid prolonged exposure in a proximity to the body. Store away from inhabited areas. |
| Color: | Black from included organic matter; pale Brown to Dark Brown in thin section. |
| Transparency: | Opaque, Transparent on very thin edges. |
| Luster: | Dull to Adamantine |
| Refractive Index: | 1.730 – 1.750 Isotropic due to fine grain size; Uniaxial ( +/- ) |
| Birefringence: | 0.000 (Isotropic) |
| Dispersion: | n/a |
| Pleochroism: | Moderate; pale yellow-brown parllel to length, medium brown perpendicular to length. |
