106 DESCRIPTIONS OF MINERALS. 
in itsrough state, 308 carats; and the ‘‘ Stewart,” which has 
a light straw color, 288°35 carats. The diamonds of South 
Africa are mostly ‘‘ off color ;” about 10 per cent. are of 
first quality ; 15, 2d; 20, 3d; and 55 per cent. are dort (W. 
J. Morton). The ‘‘Star of South Africa,” 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 ina 
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 maller 
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, im 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 1s subdivided by a 
salient angle into one irregular pentagon and two triangles. 
The ¢adle 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. 
