Now many go to the other extreme and want them over-spread. The finely cut stone lies between.
Rough
diamonds suitable for cutting to gems are of two classes: " close "
goods and " cleavage." The former are shaped naturally for immediate
preparation for cutting, as octahedrons. Formerly these were prepared
by setting two stones in handles and grinding them together, or
bruting, until a place was rounded on both where the tables should be,
but of late these points are sawed off and utilized. This is done by
charging the thin edge of a wheel with diamond dust and cutting through
the stone by rapid revolutions, as the facets are cut by pressing the
stone against the flat side of a wheel similarly charged. As soon as
this practice was established by the cutters, the Diamond Syndicate
raised the price of such rough to correspond with the value of the
pieces of diamond saved by the process.
The
polishing of a diamond is really the grinding of the stone away by
contact with the flat surface of a rapidly revolving horizontal wheel
charged with diamond dust and oil. These wheels are hackled or grooved
to hold the abrasive and the diamond being polished is pressed down
upon it, at different angles for the various facets, until the
polishing is consummated.
The
" cutting " of a diamond consists in the preparation of the stone for
the wheel, and takes the place of the old-fashioned bruting. It is done
by setting one rough stone in a turning wheel and another in a stick.
The one in the stick is then held against the other revolving in the
wheel, and they grind each other down to a girdle, from which the
stones are rounded up to a low dome for the table side, and a higher
dome for the culet
