220 



DESCRIPTIONS OF MINERALS. 



extensively as marble. The magnesian lime has been sup- 

 posed to injure soils ; but this is believed not to be the case 

 if it is air-slaked before being used. It is also employed in 

 the manufacture of Epsom salts or magnesium sulphate. 



Ankerite. Resembles brown spar, and, like that, becomes brown on 

 exposure. Fundamental from a rhombohedron of 106" 12'. It is a 

 calcium-magnesium-iron-and-manganese carbonate. The Styrian iron 

 ore beds of Saltzburg are some of its foreign localities. It occurs in 

 Nova Scotia, and in quartz veins in Western New Hampshire ; Quebec, 

 Canada, etc. 



Hydrodolomite. A calcium-magnesium carbonate containing water, 

 Pennite from Texas, Pa. , is similar. 



BARIUM and STRONTIUM. 



Barium and strontium occur in nature only in anhydrous 

 ternary compounds of the following kinds : sulphate, car- 

 bonate, silicate ; and in silicates only in combination with 

 other basic elements. The species are characterized by high 

 specific gravity, ranging from 3*5 to 4*8. Strontium gives 

 a red color to the blowpipe flame ; and barium, if strontium 

 and other basic elements are absent, a characteristic green 

 color. 



Barite. — Heavy Spar. Barium Sulphate. 

 Trimetric. In modified rhombic and rectangular prisms, 

 lAl=10l° 40'; OAfi = Ul° OS' ; OaH=127° 18'. Crys- 

 tals usually tabular. Massive 

 varieties often coarse lamellar ; 

 also columnar, fibrous, granu- 

 lar and compact. Lustre vitre- 

 ous ; sometimes pearly. Color 

 white and sometimes tinged 

 yellow, red, brown, blue, or 

 dark brown. Transparent or 

 translucent. H.=2'5-3"5. G. 

 =4-3-4-7. 



Composition. Ba 4 S, = 



Sulphur tri oxide 34-3, baryta 

 65-7=100. Strontium and cal- 

 cium are sometimes present re- 

 placing a little barium. B. B. 

 fuses to a bead which reacts 

 alkaline. Imparts a green color to the flame. After fusion 



