e cleaving of certain gem materials, such as true topaz (which splits
perfectly across the prism, parallel to its base) is easily
accomplished, and it is done in much the same manner as the cleaving of
diamond. The feldspar gems, such as moonstone, amazonite, and
labradorite, also cleave very smoothly in certain directions. Spodumene,
of which Kunzite is a variety, cleaves almost too easily to be durable.
Most gem minerals, however, lack such perfect cleavage and when it is
desired to remove imperfect parts, or to reduce large pieces to smaller
sizes, these materials are slitted as above described.

"RUBBING DOWN." The material being of nearly the dimensions of the
finished piece, the next step is to "rub it down," as it is called, to
approximately the shape and size desired. This rubbing down process was
formerly done by means of a soft metal lap (sometimes of lead), charged
with coarse emery powder and water. Carborundum, being harder and
sharper than emery, has replaced it very largely. Some of the softer
materials, such, for example, as turquoise, are rubbed down on a fast
flying carborundum wheel of similar type to those used in machine shops
for grinding steel tools. These wheels rotate in a vertical plane and
are kept wet. The laps before mentioned run horizontally. The
carborundum wheels have the grains of carborundum cemented together by
means of some binding material and this gradually crumbles, exposing
fresh, sharp cutting edges. Various sizes of grain, and various degrees
of hardness of the binding material, as well as various speeds, are
needed to suit the many different materials rubbed down by the lapidary.
Some lapidaries rub down the harder and more valuable gems such as ruby
upon diamond charged laps of brass or other metal.

CABOCHONS. The rubbing down process does not leave a facetted surface,
but only a coarse roughly rounded or flattened surface. If the material
is to be left in some one of the flat-backed, rounded top forms known as
cabochon cut, the surfaces need only to be smoothed (by means of very
fine abrasives such as fine emery applied by means of laps, or even by
fine emery or carborundum cloth), and they are then ready for
polishing.

FACETTED STONES. If, however, the stone is to be facetted in either the
brilliant form, somewhat like the diamond, or step cut or otherwise
facetted, it is cemented strongly onto a holder (much like the wooden
part of a pen holder). The upper end of the h