Kolm

A uranium-rich oil shale. "A variety of cannel coal occurring locally as lenticles in Swedish alum shales and containing 30% of ash rich in rare metals, including uranium and radium."

Mr. Jacques Jedwab reported that he examined KOLM under light & electron microscopy, in the wake of a wide project of uraniferous coals, shales, bitumens, thucholites. U-concentrations in caustobioliths develop radiation damage haloes, like in biotites, which makes them easily found under reflected light as bright diffuse features. In the kolm, the U is present as diffuse concentrations of bacterial origin, which have been studied in detail by Beda Hofmann (Chem. Geol., 1990, 81, 55-81), and which concentrate numerous metals, among which U, PGE, Pb, As, Se....

"Kolm was mined at Stora Stolan in 1909 for radium. About 200 tons of kolm with 0.5% U3O8 was obtained from 8,000 tons of [alum] shale." "The inorganic constituents of the kolm, with which the radioactivity is chiefly associated are fine-grained pyrite, carbonate and phosphate." (Heinrich (1958), Mineralogy & Geology of Radioactive Raw Materials. McGraw Hill: 491).