Chapter VII Artificial Jewelry — How Made and How Detected
MOCK DIAMONDS—“PARIS BRILLIANTS”—THE MANUFACTURE OF PASTES—FALSE RUBY, TOPAZ, SAPPHIRE, EMERALD AND CARNELIAN—HOW TO DISTINGUISH TRUE AND FALSE GEMS—IMITATION PEARL AND CORAL—ARTIFICIAL GOLD—LIST OF PRECIOUS STONES.
“Bristol Stones,” “Irish Diamonds,” “Cape May Diamonds,” and “California Diamonds,” are skillfully-cut quartz crystals. They are easily detected by the file and by their lightness.
“Paris Brilliants” are more dangerous counterfeits, and are very often sold for genuine. The great establishment of Boarguiguon, in Paris, is the most famous manufactory of artificial gems in the world, employing about one hundred hands. The gems are such perfect imitations that they can be distinguished from real stones only by the closest scrutiny of those experienced in such matters. They fail chiefly in hardness; in brilliancy and gravity they nearly or quite equal the genuine.
Nature has made the most precious stones with the most common materials. The diamond is purified charcoal; while the matter of clay and white pebbles is the base of all other gems.
The chemist has imitated nature in the production of colored gems. The base of these imitations, called “pastes,” is “strass”—a white glass compound of 300 parts of pure sand, 96 of potash, 27 of borax, 514 of white lead, and one of arsenic. The mixture is put into a crucible and kept at a high heat for 24 hours. This is the philosopher’s stone which competes with Golconda. The uncolored glass is used in making mock diamonds and white topaz. Another paste which has very great brilliancy, and, unfortunately, the same gravity as the diamond, is made by melting 100 parts of pure sand, 150 of red lead, 30 of calcined potash, 10 of calcined borax and one of arsenic, keeping the mixture melted for two or three days and then cooling very slowly. Each ingredient is separately reduced to a fine powder.
False Ruby is made by fusing together of strass one ounce and six drams, glass of antimony 37 grains, and purple of cassius one grain; then add eight parts more of strass and fuse for thirty hours; cool and remelt pieces in a blow-pipe. Or, melt five ounces of strass and one dram of manganese.
False Topaz can be made from 1008 grains of strass, 43 grains of glass of antimony and one grain of purple of cassius.
False Sapphire.—Add to eight ounces of strass 52 grains of pure oxide of cobalt.
False Emerald.—To one pound of strass add one dram of verdigris and fifteen grains of crocus martis. Or, take 2304 grains of strass, 21 grains of green oxide of copper, and one grain of oxide of chrome. Or, take an ounce and a half of rock-crystal, six drams of dry soda, two drams of dry borax, two drams of red lead, one dram of nitre, twenty grains of red oxide of iron, and ten grains of green carbonate of copper.
False Carnelian.—Strass two pounds, glass of antimony one pound, rouge two ounces, manganese one dram.
False Amethysts and Opals are manufactured; but the fine opal defies imitation, and the amethyst is too common in nature to allow much margin for the “pastes.”
In distinguishing true and false gems, no one character should be depended upon. All genuine stones will bear rough handling; if the merchant says “hands off,” refuse to purchase. Any gem worth buying is worth testing.
First: try the hardness. The file will make no impression on the diamond and ruby, and will with difficulty scratch the other gems; while the “pastes” are easily marred. All the precious stones scratch window glass, although opal will not attack common bottle glass. All imitations easily yield to sand. The sapphire is the hardest of colored gems, and opal is the softest. The emerald will hardly scratch rock-crystal; its counterfeit not at all. Topaz will scratch ordinary ruby, but will not touch sapphire.
Secondly: as to weight. This is the most accurate method, but the stone must be taken from its setting. The mode of taking the gravity has already been given (page 13), and the amount of each is stated in Chapter II. Garnet is the heaviest of gems; weighed in water it loses only one-fourth of its weight; i. e., if a red garnet be suspended by a fine thread from a delicate balance and immersed in a glass of water under it, one-quarter of its ordinary weight in air must be added to the pan from which it is suspended to restore the equilibrium. In like manner, ruby and sapphire lose a little more. The diamond and white topaz lose two-sevenths of their weight. Rock-crystal, amethyst, carnelian and agate lose five-thirteenths; and opal about one-half, being the lightest of gems. The emerald loses more than one-third.
As “paste” can be made so as to have the same specific gravity as the genuine article, this test alone can not be relied upon; but very few of the imitations are so carefully made. The test is very convenient in distinguishing gems of like color from each other, as oriental ruby, spinel ruby and red tourmaline, and green tourmaline and emerald.
Thirdly: characteristics depending on light and electricity. It is not easy to look through a diamond of the first water, while imitations readily permit objects to be seen through them. A very delicate and perfect test of a diamond, distinguishing it from all colorless gems, as white topaz, white sapphire and white zircon, but not from “pastes,” is to look through it at a pin-hole in a card. This requires some dexterity, and the gem should be fixed to a steady object by a bit of wax at a proper distance. A true diamond will show but one hole, all the others will show two. As white topaz, when large, is a magnificent stone, it is often palmed off for a diamond of great value; but this test is invariably certain.
A true diamond retains its brilliancy under water.
When a colored stone is placed in the path of the solar spectrum (the row of seven colors into which sunlight is separated by a prism), its color will vary with the portion of the spectrum which falls upon it; and two stones of the same color, but of a different nature, will exhibit different effects. Thus, a paste placed beside a fine colored gem, betrays its worthlessness. A simpler method of testing stones is to look at them through a bit of glass, colored red, yellow, blue or green. Every stone will exhibit, under this test, properties peculiar to itself, and by which its nature may be recognized. This is also a severe test for the purity of tint; for if pure and unmixed, the stone will appear completely black in every other light but its own color. Milky and turbid stones can not bear this test.
A first-class ruby has the color of the blood as it spirts from an artery. The deeper the hue of the emerald the more it is valued; it loses none of its brilliancy by artificial light. The pale rose topaz, the kind most esteemed, is artificially colored by heating it.
If topaz or tourmaline be gently heated, it becomes electric and will attract a thread or suspended pith-ball. No imitation will do this. All real gems when rubbed will attract the pith-ball, and retain the power a long time; the pastes also become electric, but soon lose their attraction. Rub a glass tube with a piece of flannel and bring it near a suspended pith-ball; the latter will be strongly attracted and then repelled. Immediately rub a genuine diamond and bring it near the ball, and it will be attracted. A paste diamond thus rubbed would repel it.
Finally: the breath remains much longer on the pastes than on real gems. The former also betray under a magnifying glass small air bubbles. Diamonds and other first-class stones are always cold to the touch.
False Pearls.—These are glass beads coated with a mixture of three ounces of scales of the blay or bleak fish, half an ounce of fine glue, one ounce of white wax and one ounce of pulverized alabaster. Powdered opal is sometimes used; also the powdered pearl of the oyster and other shells soaked in vinegar, and made up with gum tragacanth. Artificial pearls are usually brittle, and do not weigh more than two-thirds as much as the genuine.
False Corals.—These are made of resin and vermilion; or of marble powder made into a paste with varnish or soluble glass and a little isinglass, colored by Chinese vermilion, and then moulded. They are used for setting in cheap jewelry. The knife shows it to be too soft to be genuine.
Artificial Gold.—The following oroid or imitation gold is sometimes sold for the genuine article which it closely resembles. Pure copper, 100 parts by weight, is melted in a crucible, and then 6 parts of magnesia, 3.6 of sal-ammoniac, 1.8 of quicklime and 9. of tartar are added separately and gradually in the form of powder. The whole is then stirred for about half an hour, and 17 parts of zinc or tin in small grains are thrown in and thoroughly mixed. The crucible is now covered and the mixture kept melted for half an hour longer, when it is skimmed and poured out.
Any imitation of gold may be detected by its weight, which is not one-half of what it should be, and by its dissolving in nitric acid while pure gold is untouched.
Precious Stones. — Arranged According to Color and in Order of Hardness
| Limpid. Diamond, Sapphire, Topaz, Rock-Crystal. | Yellow. Diamond, Topaz, Fire-Opal. |
| Blue. | Red. |
| Sapphire, | Sapphire-Ruby, |
| Topaz, | Spinel-Ruby, |
| Spinel, | Brazilian-Topaz, |
| Aquamarine, | Hyacinth, |
| Indicolite, | Carnelian, |
| Turquoise, | Rubellite, |
| Kyanite. | Garnet. |
| Green. Oriental Emerald, Chrysoberyl, Emerald, Chrysoprase, Chrysolite, Amazon Stone, Malachite. | Violet. Oriental Amethyst, Amethyst. Black and Brown. Diamond, Tourmaline, Hyacinth, Garnet. |