noun scheelite, or calcium tungstate.
2. tungsten ·noun a rare element of the chromium group found in certain minerals, as wolfram and scheelite, and isolated as a heavy steel-gray metal which is very hard and infusible. it has both acid and basic properties. when alloyed in small quantities with steel, it greatly increases its hardness. symbol w (wolframium). atomic weight, 183.6. specific gravity, 18.