CARBON GROUP. 107 
Diamonds are employed for cutting glass; and for this 
purpose only the natural edges of crystals can be used, and 
those with curved faces are much the best. Diamond dust 
is used to charge metal plates of various kinds for jewelers, 
-lapidaries and others. Those diamonds that are unfit for 
working, are sold for various purposes, under the name of 
bort. Dryills are made of small splinters of bort, and used 
for drilling other gems, and also for piercing holes in artifi- 
cial teeth and vitreous substances generally ; and, others of 
iron set with a few diamonds, for drilling rocks. 
Graphite.—Plumbago. 
Hexagonal. Sometimes in six-sided prisms or tables with 
a transversely foliated structure. Usually foliated, and mas- 
sive ; also granular and compact. 
Lustre metallic, and color iron-black to dark steel-gray. 
Thin lamine flexible H.=1-2. G.=2°25-2°27. Boils 
paper, and feels greasy. 
Composition. Commonly 95 to 99 per cent. of carbon. 
B.B. infusible, both alone and with reagents; not acted 
upon by acids. 
Diff. Resembles molybdenite, but differs in being unaf- 
fected by the blowpipe and acids. ‘The same characters dis- 
tinguish the granular varieties from any metallic ores they 
resemble. 
Obs. Graphite (called also black lead) is found in crys- 
talline rocks, especially in gneiss, mica schist and granular 
limestone; also in granite and argillyte. Its principal Eng- 
lish locality at Borrowdale, in Cumberland, is now nearly 
exhausted. : 
In the United States graphite occurs in large masses in 
veins in gneiss at Sturbridge, Mass. It is also found in 
North Brookfield, Brimfield and Hinsdale, Mass. ; abundant 
at Roger’s Rock, near Ticonderoga ; near Fishkill Landing in 
Dutchess County ; at Rossie, in St. Lawrence County, and 
near Amity, ii Orange County, N. Y.; at Greenville, N. C.; 
’ in Cornwall, near the Housatonic, and in Ashford, Ct.; near 
Attleboro, in Bucks County, Penn.; in Brandon, Vermont ; 
in Wake, North Carolina; on Tyger River, and at Spartan- 
burg, near the Cowpens Furnace, South Carolina; aiso 
abundantly and of excellent quality in Canada, in Bucking- 
ham, Fitzroy and Grenville. 
