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GEMS

Gem Cutting

In the latter case we have the form of cutting known as the rosette or rose. A cut stone provided with facets on all sides is represented in Fig. A, a, and c being views from above and below respectively and b from the side. When such a stone is set as a jewel the side turned towards the observer is known as the upper portion 'or crown, while the opposite side or lower portion is referred to as the culasse or pavilion. The facets of the crown and of the culasse meet in the edge RR (Fig. A b), which is known as the girdle or edge, and is the portion of the stone, which is fixed in the setting. The whole forms, as it were, a double pyramid with truncated summits, each pyramid having a common base in the girdle. Of the four types of faceted stones the rose or rosette type has been already mentioned; the remaining three are known as the brilliant-cut, step-cut, and table-cut. The number, arrangement, and grouping of the facets differ in these three types, but each has a crown, a culasse, and a girdle.

These different forms of cutting, which are illustrated in Plates I-III, must now be considered more in detail. In these plates, the same figure-number is given to different aspects of the same stone, the addition of the letter a, b, or c to the figure-number indicating that the stone is represented as seen from the side, from above, or from below respectively; the same letters are also used when only one or two of the three aspects are represented. Plate 1 gives a series of forms of the brilliant, and Fig. 1 of Plate 2 belongs to the same series. The other figures of Plate II represent variations of the step-cut, while Plate 3 shows various kinds of rosettes, table-stones, and stones cut en cabochon.

The expense involved in a complicated form of cutting with regular facets, grouped in the way experience has shown to be most effective, is very considerable; such perfection in cutting is never bestowed upon cheap material, but only upon more valuable stones, which will repay the outlay. In the cutting of less, valuable stones, they receive the correct form, but the facets are reduced in number and less attention is paid to their regular and precise distribution; by these means the expense of cutting is considerably lessened though the appearance of the stone suffers.

1. The Brilliant-This form of cutting is said to have been originated by Cardinal Mazarin, and was first employed at the time this minister was endeavouring to revive the diamond-cutting industry in Paris. Mazarin caused twelve of the largest diamonds of the French crown to be cut in this form, and these stones have since been known as the twelve "Mazarins". The existence of only one of these stones, however, is now known, and the genuineness even of this is doubted. The superiority of the brilliant over all other forms of cutting for diamond and other colour less, transparent stones, and also for some, coloured stones, is now so firmly established that it is at present by far the most generally used. Only in quite exceptional cases is a good diamond cut in a form other than that of the brilliant; indeed, so generally is this form given to diamonds that they are often referred to colloquially as "brilliants". Coloured, transparent stones are very frequently brilliant cut, but not so invariably as is the case with diamonds.

The upper portion or crown, 00, of a brilliant (Fig. A) bears a broad facet, b, known as the table, while the lower portion or culasse, UU, bears a much smaller facet, B, known as the culet (or collet), both being parallel to the girdle, RR, Of other facets, those meeting the table in an edge and lying wholly in the crown of the stone, are known as star facets and are lettered d in the figure. The cross facets, lettered f, g, E, and D in the figure, meet the girdle in an edge; some lie in the crown of the stone and some in the culasse. Between the star and cross facets, which are triangular in shape, lie other larger facets having four or five edges; those which lie above the girdle are lettered a and c in the figure, while those which are below are lettered A and C; these facets are not, however, invariably present in the same number. The girdle, RR, always lies in a plane, and forms the boundary of the stone as seen in Figs. A a, and A c.

Brillant cut

FIG. A. Brilliant (triple-cut), a, view from above; b, from the side; c. from below.

Several varieties of the brilliant-cut are distinguished according to the number of facets present. The double-cut brilliant, shown in Plate 1, Fig. 1 a, b, c, has four triangular star facets arranged so that their four upper edges form the boundaries of the square table, while the four opposite angles of each lie in the girdle. The space between each pair of adjacent star facets is occupied by three cross facets, the central one of each group having the form of an isosceles triangle, and the cross facet on either side having the form of an oblique triangle. On the crown or upper portion of such a stone, therefore, there are sixteen facets besides the table; these facets are arranged in two series, hence the term "double-cut brilliant". The under portion consists of twelve triangular cross facets, which are the same in number and arrangement as the cross facets in the upper portion; between these lie four five-sided facets, intersecting the small culet in short edges.

The English double-cut brilliant, differing somewhat from the double-cut brilliant just described, is shown in Plate 1, Fig. 2 a, b, c. Here the table is the centre of an eight-rayed star, formed of eight triangular star facets, which alternate with eight triangular cross facets. The facets of the lower portion are similar to those of the ordinary double-cut brilliant (Fig. 1 c); the corner cross facets having the shape of isosceles triangles are, however, occasionally absent (Fig. 2 c).

The number of facets present in the forms of double-cut brilliants does not allow of the perfect development of the brilliancy and the play of prismatic colours of the stone. Such forms are therefore given usually to small and less valuable stones; for large stones the triple-cut brilliant is more appropriate. Here three series of facets lie one above the other on the upper part of the stone; the total of thirty-two facets, exclusive of the table, is made up of eight triangular star facets, sixteen triangular cross facets, and eight four-sided facets. The arrangement of these different facets is shown in Fig. A, and in Plate 1 Figs. 3 and 4. The under portion of the stone has also sixteen cross facets, while the small culet is surrounded by eight large, five-sided facets. The form, shown in Fig. A, and Plate 1, Fig. 3 a, b, c, in which the girdle has a roughly square outline, is now somewhat out of date; since the eighteenth century the form shown in Plate 1, Fig. 4 a, b, c, has received more favour. The facets of this form are the same in number and arrangement, but are more nearly equal in size, and the outline of the girdle approximates very close to a circle. The outline of the girdle is not, however, by any means constant, it depends largely upon the natural form of the stone before it is cut. In Fig. 5 b, c, it is oval, in Fig. 6 b, c, it is pear-shaped, and in Fig. 7 a, b, c, it is roughly triangular in outline. The last case is also noticeable from the fact that the facets, instead of being in multiples of four, are in multiples of three.

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Rafal Swiecki, geological engineer email contact
January, 2008
This document is in the public domain.


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