FLUOR SPAR. 119 
allow of its being easily injured both by dirt and 
friction. 
FLUAT OF LIME. 
194. FLUOR SPAR, or DERBYSHIRE SPAR, is a 
mineral formed by the combination of lime with fluoric acid 
(27). 
It sometimes occurs in a massive, and sometimes in a crystal" 
lized state ; the primitive form of its crystals being a regular 
octohedron (Fig. 5). Its colour is usually bluish, green, yel- 
low, whitish, or a mixture of some of these. 
When heated, this substance cracks, and shines 
brightly in the dark. But if kept hot for some time, it 
ceases to be luminous, and this property cannot be re- 
stored to it. If also two pieces be rubbed strongly to- 
gether, they become luminous in the dark. 
From this spar are made several kinds of ornamental 
vases of considerable size, columns, and toys, which, 
from being extremely varied in their colours and ap- 
pearance, and admitting of a high polish, are very 
beautiful. When a piece of fluor spar is to be wroughti 
into a vase, or any similar article, it is first carved with 
a mallet and chisel into a somewhat spherical form. 
It is then fixed to a turner's lathe, and, with great care, 
i& formed into the shape that is required. When this 
is complete, it has to be polished, which is done first 
with gritstone and pumice (108), and lastly with emery 
(58) and putty. The lathes formerly in use were worked 
by the foot; but those now adopted are worked by 
machinery, the advantage of the more steady motion of 
HLwhich has been that ornaments of much more delicate 
structure can now be formed than before. The manu- 
facture of articles from fluor spar gives employment to 
a great number of industrious families in Derbyshire. 
This mineral occurs in several parts of that county, 
where it has the name of Blue John, and where it is 
obtained from caverns at a considerable depth beneath 
the surface of the earth. It is also found in various 
countries both of the European and American conti- 
nents. 
