FLUOR SPAR. 
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hard substance, which resists every other acid, is 
obliged to yield to that obtained from fluor, and 
therefore glass, which is composed of flint united 
with an alkali, is readily corroded by it. It would 
be foreign to our purpose to enter into a chemical 
analysis of this curious substance ; nevertheless, we 
may be allowed to mention the powerful effects of 
its acid when reduced to the state of gas. A gen- 
tleman, who was amusing himself with some ex- 
periments on this fluid in a large saloon, was much 
astonished, when he entered the room the next day, 
to find that every glass had lost its polish # . 
Almost every country in Europe possesses dif- 
ferent kinds of fluor spar ; but none, we believe, 
can rival England, either in the quantity or the 
beauty of this mineral. Saxony and Bohemia are 
very rich in fluor spar, but Derbyshire and North- 
umberland are much more so. In these counties it 
appears under every variety of colour, and often in 
crystals of an extraordinary size. In the mines at 
Castleton, in Derbyshire, we meet with it in lumps 
of more than a foot in diameter, and of cubical 
crystals measuring two or three inches on every 
side. 
Fluor spar is almost always found in veins mixed 
with metallic substances, and particularly in those 
* This property in the gas has since been employed in order to 
engrave on glass, and the attempt has so far succeeded, that se- 
veral impressions, representing chemical vessels, have been struck 
off for a work lately published. 
