PHYSIOGRAPHY. 213 



Fluor. 



bowing this phenomenon. Sulphuric acid decomposes the powder of 

 the mineral, attended with the evolution of fluoric acid, which is recog- 

 nized by its property of corroding glass. Several varieties, particularly 

 the sky-blue ones, lose their color on being exposed to the light, 



2. Analysis. 



By KLAPROTH. 



Lime .... 67-75 



Fluoric acid : 32 ' 25 



3. Fluor does not enter as a regular constituent into the composition 

 of rocks. It is not very frequently found in beds. More generally it 

 occurs in veins, with other minerals, in primitive or transition rocks. 

 Very seldom it is associated with petrifactions, as the blue varieties ot 

 Derbyshire, with entrochites. 



4. The most beautiful crystals of Fluor are found at Beeralston in Der- 

 byshire, at St. Agnes and other places in Cornwall, and at Zinnwald in 

 Bohemia. Large crystals, generally twins, of the cube, of handsome 

 blue and green colors, occur at Alston in Cumberland, which frequently 

 contain water. Beautiful, dark blue, perfect crystals, having their edges 

 and angles highly replaced, have been found along with Quartz in pqr- 

 phyritic greenstone, near Gourock in Renfrewshire. Well defined crys- 

 tals of the primary form, of an apple green color, occur at Moldavia in 

 the Bannat of Temeswar. Rose red octahedrons, occasionally of great 

 magnitude, are met with near Charaouni in Savoy. The Saxon varieties 

 are generally of a cubical form, and of violet blue, or wine yellow, col- 

 ors. The compound uncleavable varieties (compact fluor) are chiefly 

 from Sirassberg and Stollberg in the Hartz, from Cornwall and Swa* 

 *len. The friable ones, (earthy Jluor,) are found in Saxony, England 

 and Norway. The chlorophane occurs at the Pednandrae mine in Corn- 

 wall, and at Ecatherineburg in Russia. Specimens from the latter place 

 have been observed to phosphoresce simply from the warmth of the hand. 



The United States have not proved very productive in handsome vari- 

 eties of Fluor. The most remarkable region in this country for the 

 present species, is situated in the State of Illinois, along the country 

 south-west from Cave rock on the Ohio for thirty miles, in Gallatin co. 

 It exists in nodular masses, disseminated through the soil, or occurs im- 

 bedded in a compact limestone. Its crystals are often large, and present 

 a diversity of colors ; the prevailing one, however, is a dark purple, al- 

 most black, but appearing extremely rich by transmitted light. The 

 darker colored varieties emit a bituminous odor when cleaved. Green 

 octahedrons, sometimes an inch in diameter, have been found imbedde^ 



