heavy spar(n = noun.substance) barite, barium sulphate, barytes - a white or colorless mineral (BaSO4); the main source of barium;
is a kind of mineral

   Native barium sulphate or barite, -- so called because of its high specific gravity as compared with other non-metallic minerals. [1913 Webster]

bitter spar, fluor spar, greenland spar, heavy, heavy cream, heavy hand, heavy handed, heavy heart, heavy hitter, heavy hydrogen, heavy lifting, heavy metal, heavy particle, heavy swell, heavy water, heavy weapon, heavy whipping cream, iceland spar, rhomb spar, spar, spar buoy, top heavy