Pitchblende and coffinite - Zálesí (Javorník) uranium mine, Czech Republic. — Photo: Jędrzej Pełka · Public domain
Coffinite
A black uranium silicate — second only to uraninite as an ore of uranium — occurring as dark incrustations.
Intro adapted from Wikipedia (CC BY-SA).
Coffinite is an IMA-recognized mineral species in the silicate class, with the chemical formula U(SiO₄)·nH₂O.
It crystallizes in the tetragonal crystal system (space group I4_1/amd). It is a member of the Zircon structural group.
Key properties: Mohs hardness 5–6; specific gravity 5.1; typically black or brown; white streak; Dull to adamantine luster; optically isotropic.
IMA symbol Cof, grandfathered status — known before the IMA’s founding, named in 1955.
Found in Colorado Plateau-type black unoxidized U{V deposits, replacing organic material in sandstone; in other sedimentary and hydrothermal vein uranium deposits.
It is found associated with Uraninite, thorite, pyrite, marcasite, roscoelite, clay minerals, amorphous organic matter.
The mineral was named to honor Reuben Clare Co±n (1886–1972), Tulsa, Oklahoma, USA, pioneer geologist in the study of uranium deposits of the Colorado Plateau.
Collections: Rare & Remarkable, Metals & Native Elements.