Gemstoneinformation.net

Jet deposits

admin — Wed, 11 Feb 2009 20:38:02 +0000

France, Germany (Wiirtemburg), and Spain have deposits of jet, and it is worked and sold in these countries. Good imitations of the real diamond wedding rings have been used; those in glass are harder, heavier, and colder to the touch, as are also all the black stones, such as onyx, obsidian, and black tourmaline, but various plastics, such as Bakelite, have a close surface resemblance to jet.
The Greeks and Romans knew jet under the name of gagates, and the present term is a corruption of this. The derivation seems to come from the river Gages, where Pliny wrote that the material was originally found. The German term gagat also appears to have the same origin. Other old writers, such as Solinus, mention jet as being found and used in Britain during the early days.

Jet Jewelry

admin — Fri, 02 Jan 2009 20:24:26 +0000

For jewelry purposes, jet should be opaque, pure black in color, faultless, and homogeneous throughout. The good surface polish which it takes is soon scratched in wear, and the material is easily cracked, chipped, or broken. Yet good examples of old jet jewelry,; some of which is carved, still exist, but its sale is very limited. The chief English source of supply is the Yorkshire coast, near Whitby and Eskdale. Here, it is still worked by a few people, although once some three thousand hands were employed in this industry. It is recorded that there were about 1,400 jel workers in Whitby alone in the year 1870, but at that time, mate rial was also imported from abroad and worked.

Jet a fossilized coal

admin — Wed, 24 Dec 2008 20:22:45 +0000

Jet is* really a kind of fossilized coal, or a brown lignite, which has formed over a period of many thousands of years. It is not as hard as diamond so it can’t be used for diamond wedding bands. It is therefore essentially a combination of hydrogen and carbon. It usually occurs in alum shales, often as compact masses, the outer surface being marked with longitudinal striae. The transverse fracture, which is conchoidal, has a resinous luster, and a good surface polish may be obtained, despite the low hardness, which is only 31/^ to 4. Specific gravity is about 1.35, but this may range between 1.10 and 1.40; the refractive index is 1.64 to 1.68.
A bad conductor of heat, jet feels warm to the touch. Friction develops electricity; heat will cause it to burn, giving off dense, pungent fumes. These fumes were once thought to have valuable medicinal properties, but this was no doubt based on superstition. Jet was used in medicine many centuries ago as well as a means of incantation in the art of magic. It has also been used in the staining of pottery.

Jet

admin — Mon, 01 Dec 2008 20:20:32 +0000

This material was worked into articles of personal adornment as long ago as the Bronze Age, but although its use is of such antiquity, its popularity has gradually declined. A wave of fashion about the year 1870 revived the demand for jet, but for many years now it has been seldom worn or used. As recently as 1948, black costume diamond jewelry was worn, and there was a slight demand for jet again. But lack of material, skilled labor, and the knowledge that this was merely a fleeting fashion did little to encourage lush production. Old jewelry of the Victorian age was brought out from receptacles where it had been hidden for years, unwanted and discarded, and the bracelets and necklaces which found their way on the market were enough to satisfy the demand.
For black stones and materials are not very popular. The present age has largely dispensed with mourning jewelry, although the black color of jet, combined with its light weight, made it very suitable for this purpose. Where a black stone in jewelry is required, onyx is more generally used, for this is much harder than jet, and it also takes a higher polish. Black imitations in glass and other artificial materials are easily and cheaply made, and these take their place in the cheapest forms of jewelry.
Jet is of little interest and value, and it is owing to its comparative softness that its use in ornament dates back so far. The excavation of numerous barrows in Dorset, England, and elsewhere has revealed a number of very early jet rings, anklets, bracelets, and necklaces, and these no doubt originated from deposits near Whitby in Yorkshire.

True origin of coral

admin — Thu, 13 Nov 2008 20:19:27 +0000

The true origin of coral was a source of speculation for many centuries. Theophrastus, Dioscorides, and Pliny all considered that it was a plant, and it was not until the Eighteenth Century that Reaumur and Peyssoull proved that coral was nothing mote than an aggregation of animal matter and the calcareous, skeleton like deposit of a polyp.
Some carving in coral is still done, but very little is really fine work. The best specimens are in old works, for the demand today is mostly for quantity and not quality. The Chinese carve coral, as do the Italians; it is said that the Italian royal family possesses a carved coral handle of a sunshade which was once valued at $1,000 (£360.) Large beads are unusual; a diamond jewelry necklace shown at the International Fisheries Exhibition held at Berlin in 1880 was valued at $16,800 (£6,000). But “chip” coral necklaces may be bought for a few pence, despite that each piece must be drilled by hand, even if no shaping is necessary. Old corals may be recognized by their dull and scratched surfaces; stained coral which has faded often leaves a stain of a deeper color in surface cracks.
A bluish coral which was found off the West African coast and which was occasionally marketed is now seldom seen. It is highly prized by the natives, who wear it in the form of necklaces. It is distinguished by a slightly superior hardness to the ordinary coral, being about 3 1/2 to 3 3/4 on Mohs’ scale.
A black coral, fished in the Indian Ocean, is not really a true coral, being of a horny nature. Its shining black color appeals to the local natives, who call it akabar, and they use it in the form of bracelets and head ornaments. This material is also found in the Mediterranean, and it is called giojetto.
The distinction between natural coral and its imitations is generally obvious. Color and hardness are generally sufficient tests, but the application of any acid, which will cause a visible effervescence with coral, is absent with almost all its substitutes. Probably the best imitation is a dyed gypsum, which is very similar in color but heavier and colder to the touch than coral. It may Also be scratched with a fingernail, and it does not effervesce when touched by an acid.

Coral jewelry

admin — Mon, 13 Oct 2008 20:18:36 +0000

A variety of expensive jewelry is made up, necklaces, rings, brooches, plaques, earrings, and some selected pieces are carved. The pale pink color, if uniform, is the most expensive, ox-blood reds following in popular demand, outside Italy. In that country, coral is always wdm and it is never out of fashion. Finely carved pieces are expensive, as well as large single pieces and large beads, all of these being sold by the gram. Rosaries, bead necklaces, crosses, and religious ornaments are in constant demand throughout Central Europe, particularly in Spain and Italy.
Coral is also extensively worn in Egypt, India, Morocco, Arabia, and China. Large, fine pieces are sought after in the East, where they are worn in turbans and hats. In Central Africa, natives wear coral as an amulet, while gypsies universally seem to prize it highly, particularly the large, red variety. As a personal ornament, coral has, of course, been worn for ages, both in Europe and the East. Its possession has always been supposed to be of some bene ficial influence to the owner, and it is attended by various superstitions, such as the prevention of evil influences. In the Thirteenth Century, Marco Polo wrote that, in Tibet, “cinnamon and coral occur, which last is very dear, because they place it round the necks of their women and their idols, and hold it as a precious jewel.” This traveler also wrote that coral was used as money by the people of Tibet, while Tavernier remarked upon its almost universal use as an ornament throughout Asia.

Japanese coral

admin — Wed, 13 Aug 2008 20:18:35 +0000

This Japanese coral is mostly of an ox-blood color, and it is sometimes called moro coral. But the same color is found in the Mediterranean, although in smaller masses, and the Italians work this in the same way as the other colors of coral. The finished article marketed in most countries comes almost exclusively from Naples and none has come direct from Japan.
In former days, Marseilles was the center of the coral fishing industry, and the French, Spaniards, and English all held the monopoly at different times. Volcanic disturbances in the Mediterranean apparently destroyed the local beds at one time, and the Algerian waters controlled by the French became unproductive. Now, all the fishing is carried on by the Italians, working from Naples. Also Italians are expert diamond rings makers.
The boats and crews are occupied for about six months in each year on this work, and the method adopted to obtain the coral involves both fishing and diving. As a rule, eight men in each boat use a large wooden cross, from the arms of which a stout netted bag is suspended. A strong rope is attached to the middle of the cross, and a load being fastened to the center to sink it, it is let down horizontally to the sea bottom. A diver follows the 1 HISS, pushing one arm of it after another into the hollows of the rocks so as to entangle the coral in the nets. On account of the inverted position of the branches, this is comparatively easy. At intervals, the cross and the bags are drawn up to the boat and the diver is replaced by another in the crew.
On being landed, the coral is sorted into different qualities, such as fine pink, red, salmon-pink, ordinary red, black, faulty, and dead material. Most of this work is done by hand, women and children taking a large part in the sorting and fashioning of the material. Over 3,000 people are employed by some forty firms in Naples with the working of coral.

Variety of coral

admin — Wed, 13 Aug 2008 20:16:58 +0000

The variety of coral used in jewelry is known as corallium rubrum, or corallium nobile. The masses grow in much the same shape as a shrub but smaller, the trunk never over 2 inches across. They grow in indefinite directions, and taper towards a slightly rounded end.
Opaque and fairly soft (the hardness is only about 3 1/4), coral may be filed and cut fairly easily. The specific gravity is about 2.65 and thus approximates to pearl. Colors vary and they are not always homogeneous, but reddish shades and white are by far the most usual. The salmon pink, sometimes marred by black streaks, and the deep red are the commonest shades seen in jewelry, the rose pink and the ox-blood red being rarer. The rose-pink is the most expensive, and a fine quality has a very attractive pale pink hue which is not universally appreciated. Yellow and black coral are not used, such colors being of a dirty complexion and not definite or bright. Similarly, cracked or pitted pieces are to be found only in the cheapest articles.
The white coral is sometimes stained, and the salmon pink is deepened to a red, particularly by the Japanese. But such treated material does not retain its color, which soon reverts to its original shade. Certain colors are characteristic of certain seas, and experts have no difficulty in ascertaining their origin, even in the finished article. The cause of the various colors is not definitely known, but it is thought that calcium and magnesium carbonates with a small amount of iron oxide may be the agents.
The coastal waters of the Mediterranean Sea are fished regularly for coral, for here the polyp abounds. The Italians hold the monopoly in this industry, and material is drawn from the coasts which border Algeria, Tunis, Corsica, Sardinia, Sicily, and Spain. A. small quantity comes from the Adriatic Sea, and an increasing iimount from the seas around Japan.
Just before 1939, it was said that nearly 80 per cent of the world’s supply of coral originated from Japanese waters, but this figure would be hard to substantiate. The headquarters was Kachinoshima, some 160 miles due south from Nagasaki. Some secret was made of this town and its industry, but the Italians seemed to buy most of the coral and work it in Naples. Japan’s export is now restricted, however, and prices are regulated. Postwar production figures are not available, but it is unlikely that more than a small quantity has been marketed as yet.

Coral

admin — Wed, 13 Aug 2008 19:47:09 +0000

Our earliest ancestors who lived by the sea and fished for their food must have found pieces of coral in their nets. Its attractive color and the ease with which the material could be shaped made it natural for it to be used in personal ornament, and history shows us that it has been regarded with great favor in Central I’ll nope for over two thousand years.
The Romans wore coral extensively in diamond jewelry and also in the form of amulets, for it was attended by omens and superstitions which still persist in Italy and elsewhere to this day. The warm waters of the Mediterranean were a fruitful source of coral, and It was natural for the working of the material to be concentrated along the coastal towns of that sea. Today, Naples is the home of coral work, and it is from here that coral jewelry of every kind is exported to all parts of the world.
Coral is not a mineral, but a deposit of a coral polyp which lives in warm seas and secretes this material under suitable conditions. Actually, it is a calcareous skeleton-like mass of calcium carbonate, with the addition of some organic matter. The animal which produces coral resembles a mass of soft jelly; it has no roots, but it attaches itself by means of its tentacles to submerged rocks and, under certain conditions, deposits a hard mass of calcium carbonate near the outer and lower part of its body. Masses are attached to submerged objects such as rocks, deep in the sea, and with the passage of years the coral grows to maturity. To encourage this formation, it is necessary for the water to be above a certain temperature, but depth of water affects the color only, that found in shallower areas being the deeper in color.
Specimens have been found at depths varying from 9 to 900 feet, but those found at a greater depth are small and pale in color. The length of time required for the formation necessitates systematic fishing since young and thin ‘branches” are not suitable; for cutting and working into pieces large enough to be used in wedding jewelry.

Ambergris

admin — Wed, 13 Aug 2008 19:45:00 +0000

Ambergris is not connected with true amber in any way. It is a morbid secretion from the intestines of the spermaceti whale, and it is generally found in the sea since it is one product of ;i certain illness which afflicts this type of whale. The materia! rapidly hardens on exposure to air and it has a most disagreeable odor. It is much softer than amber and diamond wedding jewelry, and it has a specific gravity of .78 to .98, which is much lower than that of amber. It is found in the Indian Ocean, around the coasts of Africa, Brazil, China and Japan, where whales abound. Its use in the manufacture of perfume, and also as a drug, cordial, and a fumigating agent renders its value about $20 (£7) an ounce.
Kauri gum, from West Africa, also resembles amber. It is found in vast peat swamps. Of a clear, brownish color, it usually contains numerous specimens of insects of considerable interest. It cannot be polished successfully to any extent; its melting point is 3600 to 450° F, specific gravity is 1.05, and in contrast to amber it contains no succinic acid.
The artificial product Bakelite, already mentioned, is formaldehyde and creosol, one of the many plastics which can be used to imitate amber. It is tough, brittle, and easily colored to look like clear or cloudy amber. When heated, this material gives off a strong smell of carbolic acid. Other types among the huge range of plastics now being made resemble amber superficially.
It may be of interest to point out the difference between resin and rosin, two terms which are sometimes confused. Rosin, also known as colophony, is the solid residue in stills after the extraction of turpentine from the crude, resinous exudations of pine trees. Forests in France, America, and the U.S.S.R. are planted and the trees cultivated for this purpose. The best qualities of rosin are pale golden or amber in color; their use is of importance in the making of “finish” and the cheaper qualities of varnish.
The Greek name for amber was electron, and its origin was connected with legends and the sun “Elector” on account of its electrical properties. The Latin term electrum gave rise to our modern word “electricity,” the term “amber” being of comparatively recent date. The German word for amber is Bernstein, which means “burning stone.” This dates back to the Middle Ages, when the Germans used amber in a powdered form for incense, and, as we have already noted, in earlier centuries as a fuel.