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 

 tort. Drills 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-grav. 

 Thin lamina* flexible. H. = 1-2. G. = 2 -25-2 -27. Soi'ls 

 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, in 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 ; also 

 abundantly and of excellent quality in Canada, in Bucking' 

 ham, Fitzroy and Grenville. 



