Uraninite
or PITCHBLENDE, an ore of uranium from which radium is prepared. It is found in small quantities in Cornwall (England), Austria, Colorado, Connecticut, and North Carolina. The name is derived from the German Pechblende, owing to the similarity of the mineral to pitch and zinc-blende. It is black and opaque, with a dull luster, and gives a brownish black streak on paper. It may contain as much as 88 per cent. of uranium oxide, with small percentages of other rare metals, includthanum, yttrium and erbium, the amount ing thorium, cerium, zirconium, lanof radium amounting to only one part in five million.