191 On Gems, 



on any of its interior surfaces at n grc.itrr angle of inci- 

 dence than 24^ degrees. The diamond, therefore, will not 

 onlv throw back all the light which an artilicial gem would 

 reflect, but likewise one-half as much more, which, falling 

 bet\\*een the angles of -1 1 degrees and i-li, would have been 

 suffered to pass through by the false gem. 



There are two kinds of the diamond, the Oriental and the 

 Brasilian, which differ only in the form of their crystalliza- 

 tion. 



The Oriental diamond crystallizes in octaedra, composed 

 of two pyramids having four equilateral triangular faces, a 

 little convex, united by their bases. This form is some- 

 times modified into a figure of twenty-four faces, and some- 

 times even of forty-eight, all triangular and somewhat con- 

 vex. The specific gravit\ of the Oriental diamond is 3'5i212. 

 The Brasilian diamond crystallizes in dodecaiidra, the 

 twelve faces of which are rhombs a little convex. The 

 specific gravity of this stone is 3'4444. 



The Oriental diamonds are found in the kingdoms of Gol- 

 conda, Visapour, Bengal, and the island of Borneo. There 

 are four mines, or rather two mines and two rivers, whence 

 diamonds are drawn. The mines are; 1st, That of Raol- 

 conda, in the province of Carnatica, '^WQ leagues from Gol- 

 conda and eight or nine from Visapour : it has been disco- 

 vered about 300 vears. 2d, That of Gaui or Colour, lying 

 eastward of Golconda : it was discovered about 200 years 

 ago by a peasant, who digging in the ground found a na- 

 tural fragment weighing 23 carats. 3d, That of Somelpour, 

 or rather of Gaoul, that being the name of the river in the 

 sand of which these stones arc found : this is the most an- 

 tient of them all. Lastly, The fourth mine, or rather the 

 second river, is that of Succudan, in the island of Borneo. 



The diamonds from Raoleonda are found in a rocky soil, 

 through which run several small veins of half an inch, or 

 sometimes an inch, broad, out of which the miners, widi a 

 liooked instrument, draw the sand in w hich the diamond* 

 are. When a sufficient quantitv of the earth is obtained, 

 they wash it several times to separate the stones therefrom. 

 These men work quite naked, except a cloth drawn round 

 the middle ; and besides this precaution, they have likewise 

 inspectors to prevent their concealing of stones, which they 

 frequently do by swallowing them. 



In the mine of Gani, or Colour, was found tiic famous 



diamond of Aurcng Zeb, the great mogul, which, before 



it was cut, weiirhed 7!)3 carats. The iniuers dig 12 or 14 



feet deep, and till such lime as thev find water, which serves 



1 them 



. 



