gemstonesbuy.com

Below the girdle or setting edge, which is usually not polished, is the base; this contains 24 facets, but 25 if a culet is present. The culet, or collet, is a very small facet at the base of the stone, but in modern cut stones, this is usually absent. The base thus terminates in a sharp point, but older cut stones always have a culet. Its absence eliminates the impression of a black spot at the bottom of the stone. Since the culet is generally protected when the stone is mounted in jewelry, its presence is now considered to be a disadvantage.

There are 8 five-sided facets, 4 of which are called pavilion facets and the others quoins. If no culet is present, these facets will be four-sided. The other 16 split facets are triangular in shape, and consist of 8 cross facets and 8 skill facets (also called bottom half or break facets). All these facets may be described by different names, according to the place of cutting.
The angles between the normals of facets should be 45 °. Between the table and templets, they should be about 40 °, between the culet and pavilion about 40°, between the cross facets and the table about 45 °, between the cross facets in the base and the culet about 45 °, and between the star facets and the table about 26°. Totally reflected light should come through the side facets of the crown, and not through the table. These proportions are very important in order to give the maximum brilliancy from the diamond. A well cut stone must have these definite proportions between its width and height, and the facets must be inclined at these angles. Actually, most London lapidaries make the angle between the bezel facets and the girdle 35 °, and the angle between the girdle and the pavilion facets 42 °.

Turquoise is also deepened in color by artificial means, aniline dyes being sometimes used. But the coloring matter soon fades, this type of dye being most unstable. Quartz cat’s-eye is also stained a dark blue and also pink, both unnatural colors to this stone. We have already noted that heat applied to smoky quartz, amethyst, zircon, topaz, and other stones affect their color, and that iris quartz is obtained by a dye being introduced into artificially created cracks within the material. Coral and mother-of-pearl are both stained to improve their color, aniline dyes being used. Some new coral is covered with a varnish after being colored, but this wears off in course of time.
Much of the so-called “antique” amber, and “Chinese” amber is the result of staining new material to simulate the dark brown and clear red varieties, which are much liked. The rough is immersed in oil to which coloring matter has been added, and then gently heated for some days. After being dried,  cleaned, and polished, the amber will be found to have absorbed the coloring matter, although often only superficially. Amber is very brittle, so unless the heating is carried out very gradually, the material will split or crack. The colors obtained are often very similar to the natural shades, but they are seldom permanent. Such amber is sold at an enhanced price.

A green color is sometimes seen in the clear or semiclear amber, while compressed amber, which approximates to a reconstructed amber, may be stained to any color. A green very much like that of Chinese jade is sometimes seen, but as amber is softer and lighter than any stone, there is no difficulty in distinguishing it.

The chief forms of cutting used are the brilliant cut, the step (or trap) cut, the mixed cut, the rose cut, and various forms of cabochon cuttings. Transparent stones are usually faceted; opaque and translucent stones are generally cut en cabochon. There are a number of other so-called “fancy” cuts, these being usually seen with diamonds, topaz, amethysts, aquamarines, and a few other stones.
The brilliant cut is so called because it is characteristic of the diamond. The number of the facets, their inclination to each other, and the ratio of the width to the depth of the stone are factors which have been definitely established by practice and calculation, and any departure from the acknowledged standards will lessen the brilliant effect which is such an outstanding property of this gem. If properly cut, there will be 57 facets (or 58 if a culet is present), and the brilliancy of the finished stone will depend largely upon the proportion of these facets to each other.
The girdle divides the upper part, or the crown, from the base, and it is usually circular. It is the only part of the finished stone which is generally left unpolished. If the girdle is not circular, the arrangement of the facets will be distorted. It should be as
thin as is practical but not so thin that there would be a risk of chipping when the stone is set in a mount. In order to obtain the maximum brilliancy and fire, light falling on the table (which is the broad, flat, large facet on the top of the stone) should be refracted and then reflected from the base facets, ultimately emerging from the crown facets. Additional facets are sometimes used in large stones, and their inclination might be modified to suit the optical characteristics of the particular specimen.

Of the 57 facets, 33 are contained in the crown. There is the large facet on the top surface, called the table, which is octagon shaped; 8 triangular star facets, 8 quadrilateral facets (4 templets and 4 quoins, sometimes called bezel and top main facets, or top corner facets), and 16 triangular facets (8 cross and 8 skill facets, sometimes called top half or break facets).

The special shaping and hollowing of bowls, ash trays, ink wells, and similar articles is carried out in much the same way, the stone being pressed against smaller caborundum laps. Polishing is effected by laps which are covered with tripoli powder and oil. This work is also laborious; a certain amount of heat is generated by the friction, and care must be taken not to develop or enlarge cracks within the material.

Drilling is specialized work, and requires much experience and a delicate touch. The drill is set with two specially shaped pieces of black diamond, and considerable skill is necessary to set these correctly so that they are not broken in working. The driller sets his own diamonds, their position varying according to the size of hole required. If the prevailing fashion is for beads or button earrings, the driller has a busy time. A bad driller will break his drill frequently and thus make his work unprofitable. The correct setting of the drill is therefore of the utmost importance.
Two black diamonds, which are very small in size, are selected, and these must be shaped if necessary so that they are triangular and of the same length. Constant examination with a loupe is required before they are considered satisfactory. They are then inserted in a wooden holder which is topped by a piece of lead, the lead being grooved to take the stones. They are hammered in and then tested on glass, and lead above the surface of the diamonds being filed away. Their positions in the holder are such that, when the drill is rotated, the diamonds will cut a very small circle. This circle will be deepened by the rotation of a bow until the material is bored through, the narrow core being thrown out as a powder. Although white diamond is harder than the black, it is not so tough. Fine drills are always set with two small black diamonds; larger drills may have more than two pieces inserted.

Porous stones are the easiest to treat, for they will naturally absorb any coloring matter in the form of a solution much more readily than others which have a hard texture. Such stones would not be visibly porous and their surfaces might appear to be hard and smooth. Those of a crypto-crystalline structure seem to take an artificial stain the best, for instance, chalcedony and turquoise. Staining by the introduction of coloring matter almost always involves heating the specimen as well, so it will be seen that a controlled heat is a necessary factor in this process. Experience in judging the time and the amount of heat required is necessary; gradual application is essential, otherwise the stone will crack with the sudden and unequal expansion, and flaws will develop to such an extent that the material will be spoiled. With experience, the facility with which a rough stone will take a stain and the time required for the process can be approximately judged, and with some qualities of chalcedony, those which are most suitable for staining gain a higher price in the rough than others which are not so suitable for this purpose.

Chalcedony, a type of quartz which comprises several well known semi-precious stones, is most frequently used to produce an artificially colored but real stone. All colors are introduced, blues, greens, reds, pinks, and yellows, the blues and pinks usually being the most unstable. The translucent bluish material is sold as “chalcedony,” and the pink stones as “rosaline.” Both fade fairly quickly and unevenly, and a bead necklace of such stones will show differences of shade after wearing for a short time. The translucent greens, often of a very attractive shade, are more stable; they are marketed as “chrysoprase” or “green carnelian,” both misnomers, for there is a natural chrysoprase of a green color (always different from the artificial green), and green carnelian is a contradiction of terms. These stones are stained after cutting, but “chalcedony” and “rosaline” are stained in the rough before cutting.

Up to 1939, agates and large pieces of rough stone were still worked in mills which dot the sides of the winding river Nahe. The flowing water is diverted near the mill to form a pond, and by a system of sluices, it is controlled to fall on to a large flanged wheel. This mill wheel is thus revolved by the power of the water, and another system of pulleys and belts from the wheel transmits the power to the cutting and grinding stones within the mill itself. The water is then directed back to its normal course, where it joins the main stream on its downward path. A number of stone cutting mills which border the river at intervals are thus served by the same water.

The mills are run on a co-operative system, one man being elected the foreman by the workers, who might number up to ten. The foreman deals with the merchants, who give him a certain weight of rough stone with directions as to what they require to be cut. Payment of the work is shared out on a prearranged basis, the cut stones being returned to the merchant when ready. In a few instances, it has occurred that some of the rough stone not used has been retained by the workers, with the result that cut stones at a cheap price find their way on to the market, thus leading to undercutting. The men work together and buy their own equipment, such as wheels, laps, and belts, and also rent the small hut and often a piece of adjoining ground. If necessary, they can easily get an advance from a merchant or a bank for the purchase of necessary materials. Slitting, grinding, polishing, and drilling are all separate and different operations, sometimes being carried out by different mills. Drilling is always done by one who specializes in this craft, often at home in one room set aside as a workshop.

For the sake of convenience, the stones or beads to be drilled are first set in rows on a stone slab by means of a hard wax. When drilled, these stones are knocked out of the wax with a hammer. The top of the drill is fixed in one of three holes previously drilled in an agate slab, which is held by a wooden arm. Around the arm, passes the string of the bow, about 18 inches in length. The bow is worked forwards and backwards in a horizontal direction with the right hand, the wooden arm holding the drill passing under the left arm so that pressure on the drill may be controlled. Before commencing the drilling, the surface of each stone must first be slightly roughed off or drilled in the correct position with a larger hand drill. In this drill, the diamonds would naturally be set farther apart in order to make a larger hole.

If a bead be examined, it will be seen that the bored hole will be slightly larger at the surface. While working, a fine oil is constantly applied with the forefinger to the drill so that it will not bind or get too hot. The drill must be worked straight and true, and the hole is carried straight through the material unless it is thick, when it must be worked from both sides so that it will meet and make one straight line. If the drill holes do not meet exactly, they will leave a sharp edge within the bead, and this will cause cutting and fraying of any stringing material when the beads are eventually graduated and strung as necklaces. Moreover, the beads will not hang true, an irregularity that will be quickly noticed. The work is tiring and monotonous, and if care is not exercised, the drill will be broken in the material.

When the local agates were exhausted, the merchants went farther afield and started to import stones from all known sources. The industry was at a low ebb when it was saved by the discovery of huge quantities of excellent rough agate and carnelian in the neighborhood of the river Jacuhy in Brazil. This was in the year 1825, when it is said that a number of Idar-Oberstein emigrants were traveling through this area as musicians, there being no call for their ordinary work at home.  Regular shipments of these and other stones, especially amethyst, followed, and although civil war in Brazil interrupted this business, by 1840 a good and regular supply was forthcoming. Cutting mills in Idar increased in number, the year 1859 seeing about 140 at work, employing some 1,200 polishers. Rock crystal, amethyst, citrine, and agate were in great demand, and it was some years before the call for these stones began to diminish.
Fortunately, the discovery of the opal fields in Australia at about that time gave the industry a fresh impetus, and since then, changing fashions and the discovery of further gem bearing areas have enabled the lapidaries to be kept employed. Unfortunately, wars, tariffs, and international financial depressions have had considerable effects on the fortunes of all who are employed in this trade, for although much is normally consumed in Germany itself, Idar-Oberstein lives by its export trade. The War of 1939-1945 naturally had a disastrous effect on all concerned; the English and then the huge American markets were cut off, the exploitation of the various conquered countries being of little avail. With the man power shortage, almost all the skilled craftsmen were called upon to do war work, and this unessential industry almost died out for the time being. Its recovery will be gradual; many of its members succumbed to the toll of war, no new apprentices came into the trade, and the arrangements for importing rough stones will have to be organized once more. Skilled Jewish and other refugees have settled in other countries, where they have started lapidary workshops, and they will be loathe to return to a country which has served them so badly. For the time being, the manufacture and fashioning of synthetic stones, such as ruby and sapphire, have of necessity become more prominent. The trade of cutting and polishing diamonds on behalf of Antwerp firms, a concern of considerable and growing importance in the few years preceding 1939, has now recovered to a large extent and the industry is nourishing once again, although output is restricted owing to supply difficulties.

As we have noted, stones are very seldom used in their natural form. They need shaping and polishing to bring out their full beauty, and each stone of value has to be considered individually.
If we examine any transparent gem stone which has been cut, a number of small faces, or facets, will be observed covering the surfaces. Such facets have not been ground on the stone in any haphazard manner. They are there for a purpose, and in the case of diamond, their number, their proportion to each other, and their mutual inclination should be mathematically exact if the utmost beauty of the specimen is to be revealed. With other stones, the proportion of the facets to each other and also their direction are of great consequence.

Generally, transparent white stones are so cut that their dispersive powers and their sparkling brilliance are shown to the best advantage. Colored stones are fashioned so as to bring out the full beauty of the body color, their fundamental color being, as a rule, their greatest attraction. There is seldom any advantage in faceting an opaque stone, while others possessing peculiar internal effects, such as asterism, have to be considered individually.

Ceylon is a prolific source of a great variety of gem stones, and cutting there is an old craft which has been practised for many centuries. It is largely in the hands of the Muslims. Primitive tools are used, and practice and observation are the teachers. It takes from ten to fifteen years for an apprentice to pass from the stage of cutting imitation stones to the cutting of the precious varieties. Simple hand-operated machines are used, and the fixed idea of retaining as much weight of stone as possible nearly always results in a detraction of the value of the stone when it leaves the island. This has led to many importers buying the rough stone direct instead of the finished material.

Generally, the cutting disc is a leaden plate, the edge of which is coated with an abrasive powder such as corundum or garnet, according to the hardness of the stone being worked. The plate is rotated backwards and forwards by a hand operated bow string, small stones being held in a specially shaped tool. A similar wheel, but of copper or brass, coated with a fine paste, is also used for polishing. Experience only guides the native lapidary; he uses no electric power, and apart from custom, he uses no scientific knowledge regarding the optical properties of individual stones.

We will now consider the actual forms of cutting, that is, the general shapes into which stones are cut so that their individual properties are best brought to light. At the same time, these shapes will best lend themselves to their application in mounted forms of jewelry.