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FORMS OP THE DIAMOND.
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hand,
if the gems are too thin, their beauty, elements, and general value are
likewise diminished. There is a definite proportion of thickness to the
breadth of colorless or limpid gems, whereas the cut of the colored
gems depends upon the intensity of the color.
FORMS OF THE DIAMOND.
Diamonds
were formerly cut according.to their natural fonn, and mostly in the
planes of the octahedron. They were called then point diamonds (pierres de nature, or-pointes ingenues).
The following forms aro now, more or less, adopted by the Dutch and English diamond-cutters:
A. The Brilliant. This
cut displays to greatest advantage the lustre of the diamond : it may
be considered as obtained by two truncated pyramids, united together by
one common base, the upper pyramid being much more deeolv truncated
than the lower. It is formed —a, of the crown, or that part of the stone which remains visible after the stone is mounted ; b, the collet, or lower part ; c, the girdle, or the common base for the crown and eollet ; d, the table, the plane which is formed by the truncature of the upper pyramid ; e, the bisel, that space which lies between the girdle and table ; and f, the collet-side, the
space between the girdle and collet. The English lapidaries cut the
girdle sharp, whereas the Dutch leave it broad : the crown amounts to
one third, and the collet to two thirds of the whole height of the
diamond ; the table amounts to four- ninths of the diameter of the
brilliant, whereas the eollet only needs one fifth of the (size of the
table. The table and collet are regular octagons, and the facets
occupied by the bisel are
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