# Precious Stones/Chapter 3: Cutting and Fashioning Precious Stones

CHAPTER III.
CUTTING AND FASHIONING PRECIOUS STONES.
Very few precious stones, as we receive them from the hands of nature, present the beautiful qualities for which we look in these concentrated treasures of the earth. Often they are waterworn pebbles, roughened by attrition and blows during years or even centuries of wanderings in the beds of streams and rivers. If we find them intact in their rocky homes, they are oft-times obscured with flaws and intruding matters which mar their beauty. If transparent and without speck or fracture, yet the natural forms in which crystallised gem-stones occur are but rarely adapted for direct employment in objects of jewellery. In shape or size they are awkward for such use, while many of those marvellous optical qualities which distinguish them from the crowd of commoner materials are brought into prominence only by the artificial processes of cutting and polishing. These processes convert rough crystals into shapely gems, having fine qualities of surface lustre and interior colour, and, withal, much less liable to fracture than the original stone. Now and then a perfect natural octohedron of flawless diamond or rosy spinel may be set in a ring or jewel; but such instances are exceptional, and gem-stones, in order that all their elements of beauty may be developed to the uttermost, must be cut and polished according to rule.
All the different forms into which precious stones are cut may ​be arranged into the two groups (1) those having plane surfaces; (2) those having curved surfaces: but, under special circumstances, facets or plane surfaces are occasionally associated with curved surfaces in the same specimen. The further subdivision of the two groups of forms may be tabulated thus:
| Group 1. Plane surfaces | Brilliant-cut. |
| Group 1. Plane surfaces | Step or trap-cut. |
| Group 1. Plane surfaces | Table-cut. |
| Group 1. Plane surfaces | Rose-cut. |
| Group 2. Curved surfaces | Single cabochon. |
| Group 2. Curved surfaces | Doable cabochon. |
| Group 2. Curved surfaces | Hollowed cabochon. |
| Group 2. Curved surfaces | Tallow top. |
A few words descriptive of each of these modes of cutting stones may now be given.
The old brilliant-cut, though susceptible of many small modifications as to the size of the facets, their mutual proportions and inclinations, and even their number, requires, when perfect, 58 facets thus arranged:
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | 1 Table | The "Crown," or upper part of the brilliant. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | 8 Star facets | The "Crown," or upper part of the brilliant. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | 4 Templets or bezels | The "Crown," or upper part of the brilliant. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | 4 Quoins or lozenges | The "Crown," or upper part of the brilliant. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | 8 Cross or skew facets | The "Crown," or upper part of the brilliant. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | 8 Skill facets | The "Crown," or upper part of the brilliant. |
| An image should appear at this position in the text. If you are able to provide it, see Wikisource:Image guidelines and Help:Adding images for guidance. Fig. 12. | — | The "Crown," or upper part of the brilliant. |
| 33 | | The "Crown," or upper part of the brilliant. |
Fig. 13.
1 Culet or collet 4 Pavilion facets 4 Quoins 8 Cross facets 8 Skill facets —
= The "Pavilion," or base, or under part of the brilliant.
There are thus 58 facets in a brilliant, while the "girdle" or edge bounding the widest part of the stone divides the crown from the base, and is concealed, in part at least, by the mounting or setting. This girdle must not be very thin (it is liable to be so in what are called "spread," that is, shallow, stones), for then it may become chipped and break away during mounting. If it be thick, on the other hand, the brilliancy of the stone is lessened, and its material wasted by the concealment of a good deal of it in the mount. This form of cutting is reserved particularly for the diamond—so much so, that the word "brilliant" used alone signifies a diamond cut after this fashion. Of late years the girdle of brilliants has been made to approach a circular outline; the templets and quoins are nearly of the same size, and eight star facets are cut round the culet, thus making a stone of 66 facets. Certain rules have been laid down for the relative proportions, not only of the several classes of facets in a brilliant-cut diamond, but also for the thickness of the finished stone in each and all its diameters. Thus 1-3rd of the total thickness should be occupied by the crown or upper portion above the girdle, 2-3rds being below. The table should be 4-9ths of the breadth of the stone, and the ​culet 1-6th to 1-5th of the table; but according to some modern experts, both these facets, but chiefly the former, may be reduced with advantage below these proportions. Two of the most famous diamonds of the world show large departures from the typical proportions of a brilliant: The Koh-i-nûr in its present form is far too broad for its depth or thickness; the Regent is a good deal too thick for its breadth. But the same rule of proportion, although it may hold good for such diamonds as admit of being subjected to it without extravagant loss of weight, must be modified with stones of other species, and especially with coloured stones. With colour-less topazes, sapphires, etc., the surfaces and inclinations of the facets must be modified to suit the refactive indices and other optical constants of these minerals; with coloured stones, if pale (certain alexandrites for example), greater depth must be secured; if dark in hue, then greater "spread" and less depth (deep red garnets furnish instances).
The style of cutting known as the step-cut or trap-cut is adopted for the emerald and many coloured stones. It is subject to rules of proportion far less strict than those devised for the cutting of the diamond in the brilliant form. Each species of stone needs special study, that the typical step-cut may be so modified as to bring out the full beauty of the gem. The fault most common with step-cut stones is the too great breadth of the table, for the internal reflections from the lower facets are best seen through the sloping bezels of the crown, not through the flat surface of the table. In the step-cut (fig. 14) we have then a table, two or more sloping step facets, and then the girdle, while the lower part of the stone (fig. 15) is cut into three or more sets or zones of
Fig. 14.
Fig. 15. ​diminishing steps, with an oblong square or hexagonal or octagonal culet as termination. Some trap-cut stones are brilliant cut below the girdle, or vice versâ.
The table-cut needs little description: it has a very largely developed table with bevelled edge, or a border of small facets. It is employed for covering fine gold-work and miniatures; in the sixteenth century and later it was used in Europe for much diamond-work.
Fig. 16.
The rose-cut (fig. 16) shares with the table-cut a much greater antiquity than the brilliant-cut. It may be compared with the latter by supposing the table to be replaced by six triangular or star facets, and the crown to be represented by eighteen triangular cross and skill facets which together constitute what the French call la dentelle. The base is either flat or a duplicate of the upper part.
The other forms given to faceted stones are not of sufficient importance to need description; the star-cut and the pendeloque may just be named as patterns sometimes followed in the cutting of diamonds.
Fig. 17.
Fig. 18.
Translucent and opaque stones are commonly cut en cabochon (fig. 17); the opal and the turquoise are characteristic examples. The moonstone, avanturine, cat's-eye, and star sapphire, too, would not show their peculiar properties were the confusing reflected lights from facets to be mingled with the white sheen, the brilliant spangles, the silver thread, or the six-rayed star which these stones respectively present when properly fashioned. The one transparent stone which is frequently cabochon-cut is the garnet, which is then called a carbuncle. A variety of cabochon used for this gem is ​somewhat hollowed behind (fig. 19), to receive a piece of foil as well as to lessen the depth of colour in very dark stones. Our figures represent the simple cabochon (fig. 17), the double cabochon
Fig. 19.
Fig. 20.
(fig. 18), the hollowed (évidé) cabochon (fig. 19), and the flattened form much used for opals, and called tallow-topped (fig. 20). The double cabochon is usually cut with the base of lesser curvature than the crown; but with many stones a more brilliant play of coloured light within the stone may be secured by reversing these proportions. Although the cabochon form is almost essential to many precious stones, and is useful to hide the poverty and flaws of others, and also is convenient in the case of stones to be used in the decoration of vases and other objects to be handled, yet it ought not to be allowed to displace the various faceted forms. Doubtless there is a quiet beauty and richness in a good cabochon ruby, sapphire, emerald, or jargoon, but we lose some of the most striking characteristics of these gems when we so cut them as not to admit of the display of their dichroism, and their dispersive and reflective powers. The narrow view that all faceted stones are vulgar is based on caprice and ignorance; it is the mere unintelligent whim of a clique of artists and amateur writers on art. For the faceting of the great majority of transparent stones is an operation necessary for the development of those optical qualities upon which the beauty of precious stones mainly depends. It should be performed in strict accordance with certain rules of proportion, which may be deduced from the optical constants of each species of stone.
Information as to the mechanical processes and the materials employed in the cutting and polishing of precious stones may be found in the works of Jannettaz and Dieulafait. Horizontal wheels of steel, gun-metal, copper, lead, pewter, tin and wood ​charged with various grinding and polishing powders, are employed for different stones, and in different stages of the operations. The wheel, or disc, or lap as it is called, is usually horizontal and is made to revolve with great rapidity. The grinding or polishing powder, mixed, according to its nature, with olive oil or water, becomes partially embedded in the lap. This powder, in the case of diamonds, must be of diamond itself, generally in the form of boart, a dark and rather porous variety of the mineral. The comparatively new and artificial compound of silicon and carbon known as carborundum is now largely used in the case of the harder stones, but emery, garnet-powder, tripolite, rotten stone, jeweller's rouge, pumice, putty-powder, and bole are in constant requisition for the grinding and polishing of stones less hard than the diamond. The whole subject of this mechanical treatment of stones, including splitting, dividing and shaping operations, is one which cannot be discussed here, involving as it does a large number of minute technical details of no interest from an artistic standpoint.
This work is in the public domain in the United States because it was published before January 1, 1930.
This work may be in the public domain in countries and areas with longer native copyright terms that apply the rule of the shorter term to foreign works.
Public domainPublic domainfalsefalse