This was accomplished either in the presence of short wave ( 2540 ?) fluorescent light, where the dull white fluorescence distinguishes it from scheelite ( fluoresces blue ) and zircon ( fluoresces yellow ), or by first boiling the impure sample in hydrochloric acid to induce an oxide surface on scheelite and permitting handpicking under visible light.
42.
"' Scheelite "'is a calcium tungstate mineral with the chemical formula radium paint in the same fashion as was zinc sulphide, and Thomas Edison invented a fluoroscope with a calcium tungstate-coated screen, making the images six times brighter that those with barium platinocyanide; the latter chemical allowed R�ntgen to discover X-rays in early November 1895.
