68 Diamond Polishing
instead
of the concave or convex form of the natural stone. The dust or diamond
powder which falls is received in a square box, containing oil, and
the powder is burnt before being used, to free it from the particles of
cement that become mixed with it. By this means two facets are cut on
two different stones at the same time. During the cutting, the workman
examines the facets by means of moistening the stone with the tongue,
first taking care to remove any powder with a camel's-hair pencil. When
the facet is formed, the cement is heated, and the diamond taken out,
and replaced so as to expose a different surface until the cutting is
completed. It must be understood that by this operation only the
general outline of the form is made. A stone which would have when
quite completed fifty-eight facets, including the table and culet,
receives in cutting only eighteen, eight of which are the surfaces of
an octahedron or double pyramid, and are formed by the taking away
eight edges or angles of these eight surfaces, one for the whole table,
and one for the culet.
Diamond Polishing.
By
the next process the diamond is not only polished, but the remaining
facets are formed. This is done by means of diamond powder, on a steel
disk, called " skaif," which is made to revolve at a very high degree
of velocity, by means of steam- or horse-power. These wheels,
or"skaifs," are prepared in the following man-
