pavilion.
The plane on which they join, and which represents the greatest breadth
of the stone, is the girdle. The flat top of the upper pyramid is known
as the table. It should be four-ninths of the breadth of the stone..
The corresponding termination of the lower pyramid is known as the
culet, and this should have an area one-sixth to one-fifth of that of
the table. The number of facets given these pyramids varies with
different cuttings; but the typical has fifty-eight, which have
individual names, as indicated in the diagram.
The
outline of the brilliant cut is not always so nearly circular as in the
form shown in the diagram, although this is usual. Brilliants
are sometimes cut so as to have a nearly square outline, or again they may be made triangular, or again oval.
The
proportions of the brilliant above given are not always followed by
lapidaries, if it is deemed that they would involve the loss of too
much material, or if the cutter believes it possible to improve the
effect of the stone by departing from them. The former consideration
has weighed most largely in the cutting of some celebrated diamonds,
with the result that according to some critics the stones do not show
to the best advantage. Thus the Kohinoor diamond in its present form is
said to be too broad for its depth, and the Regent too thick for its
breadth.
The
second cutting to be noted is the trap or step cut. This is a favorite
form of cutting for colored stones. It is a shallower cutting than the
brilliant, and has a broader table. The outline is commonly oblong, in
contrast to the more nearly circular form of the brilliant, although
quadrilateral, hexagonal, and other outlines may be given. The rules of
proportion are far less strict than those applied to the brilliant. The
following form is a common one, however: Beginning with the table
above, two sloping or step facets lead to the girdle, below which three
to five or more sets, or zones of diminishing steps, extend to the
culet. The latter has the general shape of the stone. The number of the
facets is often increased over the above with advantage. A common fault
with the step cut comes from making the table too broad, since the
internal reflections from the lower facets are best seen, as Church
states, through the sloping bezils of the crown, not through the flat
surface of the table. The mixed or brilliant top cut is a combination
of the brilliant and step cut.
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