STRONTIANITE  , a

mineral consisting of strontium carbonate, SrCO3 . It takes its name from Strontian in Argyllshire, where it appears to have been known as far back as 1764, but it was not recognized as a distinct mineral until later, when the examination of it led to the discovery of the element strontium . It crystallizes in the orthorhombic system and is isomorphous with aragonite and witherite . Distinctly developed crystals are, however, of rare occurrence; they are usually acicular with acute pyramid-planes and are repeatedly twinned on the prism . Radiating, fibrous or granular aggregates are more common . The colour is white, pale green or yellowish brown . The hardness is 31 and the specific gravity 3.7 . Strontium is sometimes partly replaced by an equivalent amount of calcium . The mineral occurs in metalliferous veins in the lead mines of Strontian in Argyllshire, Pateley Bridge in Yorkshire, Braunsdorf near Freiberg in Saxony; abundantly in veins in calcareous marl near Munster and Hamm in Westphalia; and in limestone at Schoharie in New York . It is used for producing red fire in pyrotechny and for refining sugar . (L . J .