I Break Three Times Into Diamonds 161
cemented
into a wooden stick in such a manner that the plane of cleavage lies
parallel with the length of the stick. The cleaver next holds a steel
blade against the diamond in an appropriate position. One sharp short
blow with a mallet delivered upon the back of the steel blade
immediately divides the stone in the required way. As you can imagine,
no little judgment is required when perhaps a matter of several
thousand pounds depends upon a single blow.
Apart
from this method there is another way of dividing diamonds into
several pieces. Of late years the saw has frequently taken the place of
a cleaver. It is a long process, however, for a good-sized stone takes
anything from two to three weeks to cut through. The process is roughly
this. First of all the stone to be sawed is notched, and into the notch
is inserted a small thin metal disk the edge of which has previously
been treated with diamond powder. An electric motor is started and the
disk is set rotating at high speed until the stone is divided.
High-grade
stones are always cleaved and not sawn, and all cleaved stones, grade
for grade, are of greater lustre than sawn stones. Even experts have
sometimes been puzzled by this fact, when to my mind there is no
difficulty in finding an explanation. For obviously the complete
crystal, cut along the natural line of fission, diffuses the light rays
much better than the incomplete crystal of the sawn stone.
Why, then, saw diamonds at all? Precisely because in sawing no account need be taken of the line of cleavage
