106 DESCRIPTIONS OF MINERALS. 



in its rough state, 308 carats ; and the " Stewart," which has 

 a light straw color, 288*35 carats. The diamonds of South 

 Africa are mostly "ofE color;'" about 10 per cent, are of 

 first quality ; 15, 2d ; 20, 3d ; and 55 per cent, are bort (TV. 

 J. Morton). The ••Star of South Africa, 7 ' of pure water, 

 weighed 83*5 carats. Some crystals crack to pieces after 

 being exposed to the air awhile. 



The diamond is cut by taking advantage of its cleavage, and 

 also by abrasion with its own powder. The flaws are some- 

 times removed by cleaving it. Afterwards the crystal is fixed 

 to the end of a stick of soft solder when the solder is in a 

 half -melted state, leaving the part projecting which is to be 

 cut. A circular plate of soft iron is then charged with the 

 powder of the diamond, and this, by its revolution, grinds 

 and polishes the stone. By changing the position, other 

 facets are added in succession till the required form is ob- 

 tained. Diamonds were first cut in Europe, in 1456, by Louis 

 Berquen, a citizen of Bruges ; but in China and India, the art 

 of cutting appears to have been known at a very early period. 



By the above process, diamonds are cut into brilliant, rose 

 and table diamonds. The brilliant has a crown or upper 

 part, consisting of a large central eight-sided facet, and a 

 series of facets around it ; and a collet, or lower part, of py- 

 ramidal shapes, consisting of a series of facets, with a mailer 

 series near the base of the crown. The depth of a brilliant 

 is nearly equal to its breadth, and it therefore requires a 

 thick stone. Thinner stones, in proportion to the breadth, 

 are cut into rose and table diamonds. The surface of the 

 rose diamond consists of a central eight-sided facet of small 

 size, eight triangles, one corresponding to each side of the 

 table, eight trapeziums next, and then a series of sixteen tri- 

 angles. The collet side consists of a minute central octagon, 

 surrounded by eight trapeziums, corresponding to the angles 

 of the octagon, each of which trapeziums is subdivided by a 

 salient angle into one irregular pentagon and two triangles. 

 The table is the least beautiful mode of cutting, and is used 

 for such fragments as are quite thin in proportion to the 

 breadth. It" has a square central facet, surrounded by two 

 or more series of four-sided facets, corresponding to the sides 

 of the square. 



Diamonds have also been cut with figures upon them. As 

 early as 1500, Charadossa cut the figure of one of the Fathers 

 of the church on a diamond, for Pope Julius II. 



