allization of the carbon is due
to a very high temperature and tremendous pressure acting on the carbon
in a liquid form deep down beneath the earth's surface. The crystals,
intermingled with much foreign matter, are afterward projected upward,
filling these great volcanic pipes.

In order to produce the most beautiful effect, diamonds are usually cut
into one or another of three different forms, namely, rose, table, and
brilliant, the shape and size of the stone determining which form is
best. The double-cut brilliant is the most common form at the present
day. The general form of rough, crystallized diamonds is that of two
square pyramids joined at their bases. The crystals are oftenest found
octahedral and dodecahedral--that is, eight and twelve sided, and the
diamond-cutter takes advantage of these forms in shaping the diamond.

The modern lapidary must have a perfect knowledge of optics and be a
skilful stone-cutter. The numerous planes or faces which he cuts on the
surface of the diamond are called facets. In the treatment three
distinct processes are utilized--cleaving, cutting, and polishing. The
lapidary must study the individual character of each stone and determine
whether to cleave or grind off the superfluous matter so as to correct
flaws and imperfections. All this calls for the judgment which comes
only with long experience, for if the cutter errs he may ruin a
priceless gem.

The grinding and polishing are done by diamond dust mixed with oil
spread on the upper surface of a grooved flat steel wheel revolving
horizontally. The diamond, having been set in fusible solder, is firmly
pressed against the surface of the wheel by a small projecting arm and
clamp. When one facet has been finished, the diamond is removed from the
solder and reset for grinding another facet. Thus the workman continues
until the grinding and polishing are completed. Infinite patience and
steadiness of nerve, as well as steadiness of hand, are required for
such delicate and exact work. Sometimes two uncut stones are cemented
into the ends of two sticks. Then the operator, using these sticks as
handles, presses the stones against each other with a rubbing motion,
the surface of the stones being coated over with diamond dust and oil to
accelerate the process.

The last cutting of the celebrated Kohinoor diamond cost forty thousand
dollars. One may understand, therefore, that the expense of cutting a
large diamond adds materially to