such
a direction as to bring out this quality in the highest degree.
Similarly tourmaline, because of its dichroic properties, may make a
dark and uninteresting stone if cut at right angles to the
crystal-lographic axis, while if cut parallel to this axis it will make
a brilliant appearance and show two colors. Such stones as moonstone,
labradorite, tiger's-eye, and others, which show chatoyancy only in
certain directions, must obviously be cut with reference to this
feature. In transparent stones, the angle which the upper and lower
facets make with each other should be a definite one, so as to reflect
the light in the best possible manner.
Considering
briefly and in order the forms of cutting above mentioned, we may note
first the brilliant. The brilliant cut is said to have been invented by
Cardinal Mazarin in his endeavors to introduce the art of
diamond-cutting into France. It is now the form most commonly given
diamonds and is employed for many other transparent stones as well. As
will be seen from the above figure, it is made up essentially of two
truncated pyramids joined by their bases, the upper pyramid leaving
one-third and the lower pyramid two-thirds of the length of the stone.
The upper pyramid is called the crown, the lower the
44
