DIAMONDS AXD CARBONS IN BRAZIL 273 



Lying true color can be determined, but to make the stones marketable 

 abroad where this is unknown, recourse is had to heating them red hot 

 and pouring on a chemical when the crust is consumed and the real 

 color appear-. 1 have seen apparently dirty red, green, brown, blackish 

 and vellow stones after burning turn out to be pure whites and blue 

 whites. Stones so treated lose in weight about one per cent., and 

 those with cracks or defects frequently break to pieces. 



The largest authentic Brazilian diamond ever found is the famous 

 'Estrella do Sul ' (Star of the South). It weighed 254.5 carats in 

 the rough, and cut and polished weighs 124% carats, with a value of 

 $450,000. The greater number of diamonds found are less than one 

 carat; the average weight is about two carats, while a stone of 10 carats 

 is a great exception. 



Carbons which occur along with diamonds are very ordinary look- 

 ins: stones and would be refused as a present bv any one not well 

 acquainted with them. Their history is very obscure. Other than 

 a few small ones found in Minas Geraes, and those are of poor quality, 

 Bahia is the only known place where they occur. They seem to have 

 been known in 1848, when a Frenchman traveling through Bahia 

 bought them for twenty-seven cents a carat under the name of ' fer- 

 ragens' (iron stones). In March, 1856, Mr. Domingos Gomez, of 

 Boncador, took to London 6,475 carats, which he had bought for sixty 

 cents a carat, and was more than pleased to sell them at $1.25 a carat. 

 At that time their sole use was to be pounded to dust for use in dia- 

 mond polishing. 



The later history of the carbon is the history of the so-called dia- 

 mond drill which now constitutes their principal use. For this pur- 

 pose stones weighing from 1% to 4 carats are desired and larger stones 

 have to be broken to these sizes. The drill consists of 6 or 8 carbons 

 set in a crown or cylinder of steel forming the bit. They are set in 

 such a way that they alternately slightly project beyond the inner 

 and outer edge, thereby cutting as they are rotated a core, which is 

 brought to the surface from time to time as desired. Being the hardest 

 known material they will cut the most refractory ores or stones. 



As the drill goes around the carbons wear off and have to be from 

 time to time reset, until finally they become so small as to be useless. 

 For this reason, unlike the diamond whose chief use is for adornment, 

 the number of carbons is constantly growing less while the demand 

 is' exceeding production. With the perfection of the drill and its great 

 use in cutting tunnels, mines, canals, etc., the price of carbon has 

 steadily gone up from $17 a carat in 1892 to $60 to-day in New York 

 for the best quality of proper size, and the price obtained at the mines 

 has been a fair equivalent. 



The average weight of carbons encountered is much larger than 



VOL. LXIX. — 18. 



