THF. DIAMOND. 81 



green, brown or black. Luster adamantine. Transparent ; 

 translucent when dark colored. H = 10. Gr = 3*48— - 

 3-55. 



Composition. Pure carbon. It burns and is consumed at 

 a high temperature, producing carbonic acid gas. Exhibits 

 vitreous electricity when rubbed. Some specimens exposed 

 to the sun for a while, give out light when carried to a dark 

 place. Strongly refracts and disperses light. 



Dif. Diamonds are distinguished by their superior hard 

 ness ; their brilliant reflection of light and adamantine luster 

 their vitreous electricity when rubbed, which is not afforde 

 by other gems unless they are polished ; and Tby the prac 

 ticed ear, by means of the sound when rubbed together. 



Obs. Diamonds occur in India, in the district between 

 Golconda and Masulipatam, and near Parma, in Bundel- 

 cund, where some of the most magnificent specimens have 

 been found ; also on the Mahanuddy, in Ellore. In Borneo, 

 they are obtained on the west side of the Ratoos mountain, 

 with gold and platina. The Brazilian mines were first dis- 

 covered in 1728, in the district of Serra do Frio, to the north 

 of Rio de Janeiro ; the most celebrated are on the river 

 Jequitinhonha, which is called the Diamond river, and the 

 Rio Pardo ; twenty-five to thirty thousand carats are export- 

 ed annually to Europe from these regions. In the Urals of 

 Russia they had not been detected till July, 1829, when 

 Humboldt and Rose were on their journey to Siberia. The 

 river Gunil, in the province of Constantine, in Africa, is re- 

 ported to have afforded some diamonds. In the United 

 States, the diamond has been met with, in Rutherford county, 

 North Carolina, (fig. 4,) and Hall county, Georgia. 



The original rock in Brazil appears to be either a kind of 

 laminated granular quartz called itacolumite ; or a ferruginous 

 quartzose conglomerate. The itacolumite occurs in the Urals, 

 and diamonds have been found in it ; and it is also abundant 

 in Georgia and North Carolina. In India, the rock is a 

 quartzose conglomerate. The origin of the diamond has 

 been a subject of speculation, and it is the prevalent opinion 

 that the carbon, like that of coal, is of vegetable origin. 

 Some crystals have been found with black uncrystallized 

 particles or seams within, looking like coal ; and this fact 

 has be.en supposed to prove their vegetable origin. 



How is the diamond distinguished ? What are its principal localities] 



