COMPOUNDS OF CALCIUM. 209 



easily, with sulphuric acid and heat, a gas that corrodes 

 glass. 



Obs. Fluorite occurs in gneiss, mica schist, clay slate, 

 limestone, and sparingly in beds of coal either in veins 

 or occupying cavities, or as imbedded masses. It is the 

 gangue in some lead mines. 



Cubic crystals of a greenish color, over a foot each way, 

 have been obtained at Muscolonge Lake, St. Lawrence 

 County, N. Y. ; near Shawneetown on the Ohio, a beautiful 

 purple fluor in grouped cubes of large size is obtained from 

 limestone and the soil of the region ; at Westmoreland, ]\ T . 

 H., at the Notch in the White Mountains, Blue Hill Bay, 

 Maine, Putney, Vt., and Lockport, 1ST. Y., are other locali- 

 ties. The cldoropliane variety is found with topaz at Trum- 

 bull, Conn. 



In Derbyshire, England, fluor spar is abundant, and hence 

 it has received the name of Derbyshire spar. It is a com- 

 mon mineral in the mining districts of Saxony. 



Calcium fluoride also exists in the enamel of teeth, in 

 bones and some other parts of animals ; also in certain parts 

 of many plants ; and by vegetable or animal decomposition 

 it is afforded to the soil, to rocks, and also to coal beds in 

 which it has been detected. 



Massive fluor receives a high polish, and is worked into 

 vases, candlesticks and various ornaments, in Derbyshire, 

 England. Some of the varieties from this locality, consist- 

 ing of rich purple shades banded with yellowish white, are 

 very beautiful. The mineral is difficult to work because 

 brittle. Fluor spar is also used for obtaining hydrofluoric 

 acid, which is employed in etching. To etch glass, a pic- 

 ture, or whatever design it is desired to etch, is traced in 

 the thin coating of wax with which the glass is first covered ; 

 a very small quantity of the liquid hydrofluoric acid is then 

 washed over it ; on removing the wax, in a few minutes, the 

 picture is found to be engraved on the glass. The same 

 process is used for etching seals, and any siliceous stone 

 will be attacked with equal facility. This application of 

 fluor spar depends upon the strong affinity between fluorine 

 and silicon. Fluor spar is also used as a flux to aid in re- 

 ducing copper and other ores, and hence the name fluor. 



