THE NONMETALLIC MINEKALS. 279 



4. WlTHERITE. 



This is a carbonate of barium of the formula BaCO 3 , = baryta 

 77.7 per cent, carbon dioxide 22.3 per cent. Color, white to yellow 

 or gray, streak white; translucent. Hardness, 3 to 3.75; specific 

 gravity, 4.29 to 4.35. When crystallized, usually in form of hexagonal 

 prisms, with faces rough and longitudinally striated. Common in 

 globular and botr} T oidal forms, amorphous, columnar, or granular in 

 structure. The powdered mineral dissolves readily in hydrochloric 

 acid, like calcite, but is easily distinguished from this mineral by its 

 great weight and increased hardness, as well as by its vitreous luster 

 and lack of rhomboidal cleavage, which is so pronounced a feature in 

 calcite. From barite, the sulphate of barium, with which it might 

 become confused on account of its high specific gravity, it is readily 

 distinguished by its solubility in acids as above noted. From stronti- 

 anite it can be distinguished by the green color it imparts to the 

 blowpipe flame. 



Localities and mode of occurrence. The mineral occurs apparently 

 altogether as a secondary product filling veins and clefts in older rocks 

 and often forming a portion of the gangue material of metalliferous 

 deposits. The principal localities as given by Dana are Alston Moor, 

 Cumberland (Specimen No. 67923, U.S.N.M.), where it is associated 

 with galena. In large quantities at Fallowfield near Hexain in North- 

 umberland; at Anglezarke in Lancashire; at Arkendale in Yorkshire, 

 and near St. Asaph in Flintshire, England. Tarnowitz, Silesia; 

 Szlana, Hungary; Leogang in Salzburg; the mine of Arqueros near 

 Coquimbo', Chile; L. Etang Island; near Lexington, Kentucky, and 

 in a silver-bearing vein near Rabbit Mountain, Thunder Bay, Lake 

 Superior. 



Uses. The mineral has been used to but a slight extent in the arts. 

 As a substitute for lime it has met with a limited application in mak- 

 ing plate glass, and is also said to have been used in the manufacture 

 of beet sugar, but is now being superseded by magnesite. 



5. STEONTIANITE. 



This is a carbonate of strontium, SrCO 3 , = Carbon dioxide 29.9 

 per cent; strontia 70.1 per cent. Often impure through the presence 

 of carbonates and sulphates of barium and calcium. Colors, white to 

 gray, pale green, and yellowish. Hardness 3.5 to 4. Specific gravity 

 3.6 to 3.7. Transparent to translucent. When ciystallized often in 

 acute spear-shaped forms. Also in granular, fibrous, and columnar 

 globular forms. Soluble like calcite in hydrochloric acid, with effer- 

 vescence, but readily distinguished by its cleavage and greater density. 

 The powdered mineral when moistened with hydrochloric acid and 

 held on a platinum wire in the flame of a lamp imparts to the flame a 

 very characteristic red color. 



