COMPOUNDS OF POTASSIUM AND SODIUM. 223 



Y., are other localities. A handsome fibrous variety occurs 

 at Franktown, Huntingdon County, Pennsylvania. Sicily 

 affords fine crystallizations associated with sulphur. 



The pale shy-blue tint, so common with the mineral, gave 

 origin to the name celestite. 



Celestite is used in the arts for making the nitrate of 

 strontia, which is employed for producing a red color in fire- 

 works. 



Strontianite. — Strontium Carbonate. 



Trimetric. /a/=117° 19'. Cleavage parallel to I, near- 

 ly perfect. Occurs also fibrous and granular, and sometimes 

 in globular shapes with a radiated structure within. 



Color often a light tinge of green; also white, gray, and 

 yellowish brown. Lustre vitreous, or somewhat resinous. 

 Transparent to translucent. H.=3*5-4. G. =3*6-3*72. 

 Brittle. 



Composition. Sr 3 C = Carbon dioxide 29 '7, strontia 

 70-3= 100. A small part of the strontium is often replaced 

 by calcium. B.B. swells, throws out little sprouts, but 

 does not fuse. Colors the flame bright red, and after heat- 

 ing possesses an alkaline reaction. Effervesces in cold di- 

 lute acid ; sulphuric acid gives a precipitate of strontium 

 sulphate. 



Diff. Its effervescence with acids distinguishes it from 

 minerals that are not carbonates ; the color of the flame 

 before the blowpipe, from witherite and all other carbon- 

 ates ; calcium salts also give a red color to the flame, but 

 the shade is yellowish, and less brilliant. 



Obs. Strontianite occurs in limestone at Scoharie, N". Y., 

 in crystals, and also fibrous and massive; and in Jeffer- 

 son County, N. Y., and Mifflin County, Penn. Strontian 

 in Argyleshire, England, was the first locality known, and 

 gave the name to the mineral and the metal strontium. It 

 occurs there, with galenite, in stellated and fibrous groups 

 and in crystals. 



This mineral is used for preparing the strontium nitrate. 



POTASSIUM and SODIUM. 



Potassium and sodium occur in nature in the state of 

 chloride, sulphate, nitrate, and carbonate, and are constitu- 

 ents in many silicates. 



