carat vary in price from £4 to 12, but the value does not, like that of the ruby, increase enormously in proportion to its size. Mr. G. S. Streeter, who described the Burma ruby mines, mentions an Indian sapphire weighing originally 225 carats, and worth £7,000 to £8,000. Small rubies and sapphires are largely used for bearings in watches. In the United States alone about 1,200,000 watches with jewelled works are manufactured annually, requiring 12,000,000 jewels, of which 5,000,000 are ruby and sapphire, the remainder being garnets. Rubies and sapphires were obtained to the value of about £3,701 in 1902 from shallow diggings in Siam. Small quantities of sapphires are also obtained from alluvial workings in Ceylon. At Anakie, Queensland, in 1902, some £5,000 worth of sapphires were raised. Sapphire, corundum, and emery are of frequent occurrence in the United States. In Montana sapphires are largely mined; they occur in an eruptive dyke in limestone. The various localities are enumerated by Mr. J. H. Pratt in a recent report to the United States Geological Survey. Sapphires are not in great demand for the moment. chiefly because they do not appear to advantage in artificial light, but seem dark and dull. In experimenting on the action of various rays on rubies, Chaumet ascertained that the Siamese stones are of scarcely appreciable fluorescence under violet light, while all the valuable Burmese rubies are intensely fluor

escent.

Emery, the common form of corundum, is found in large quantities in the Island of Naxos, and the mines are the property of the Greek Government. The Naxos emery is superior to that of Asia Minor owing to its great density, and the greater fineness and hardness of its grain. It fetches 112 to 115 francs a ton. The world's consumption of emery is 25,000 tons annually, of which Asia Minor supplies some 18,000 tons, valued at £53,000; Canada 388 tons, valued at £10,914; and Naxos 6,328 tons, valued at £26,830.

Owing to the great value of the ruby, other stones are frequently described as such in commerce, notably the deep red spinel or the pale rose tinted Balas ruby, which is composed of alumina and magnesia, coloured by iron or chromium. When of fine colour it is a valuable stone. Spinels are derived chiefly from Ceylon, where they are found in alluvial deposits. Red tourmaline is sold as Siberian ruby, and Journal of the Society of Arts, vol. 37, p. 266,

garnet is sometimes passed off as ruby. Topaz of a pink colour is sold as Brazilian ruby. Similarly cyanite, a silicate of alumina, found in Brazil and India in blue crystals, and cordierite, found in blue crystals in Ceylon, and characterised by its dichroism, are sometimes sold as sapphires.

Emerald.-Emerald is rarely found in detrital material, but usually in situ in mica schist or limestone. Beryl, aquamarine, and emerald are silicates of aluminium and glucinum. The deep green emeralds have now become scarce and have greatly increased in public favour. The beryl is fairly abundant. The less transparent stones are of no great value, but occur in masses of large dimensions in many localities in the United States; the finest are from Siberia, Madras, and Brazil. The celebrated emerald locality in Norway was recently taken up by the Norwegian and General Exploitation Company, Ltd. (capital issued £75,000). Quantities of beryl have been found, but no valuable emeralds.

The top

In the Republic of Colombia the Muzo Mine, recently offered for sale, has been famous since the year 1555, for the production of the finest emeralds of the world. The mode of working is similar to that adopted in Europe in large quarries. soil is removed by washing until the slate rock is left bare, this being cut away by means of long bars, and with the aid of blasting. The stones are found chiefly in pockets, but occasionally some are found isolated from the veins. The large amount of débris resulting, is carried away by means of discharges of water from reservoirs at an elevation above the workings, by means of syphons. The stones, after extraction, are classified into six qualities. The greater quantity are forwarded to British India to be cut, and afterwards the better qualities return to the markets of Europe for sale. The decrease in the world's output of emeralds during the past few years has been such as to cause grave concern among the precious stone dealers. Unless new mines are discovered soon, it is not unlikely that emeralds will become the rarest precious stones in the world. As the condition of the market is now, they are worth (in stones larger than five carats) from two to ten times as much as diamonds. Several stones now in the hands of New York dealers are worth from £3,000 to £10,000 apiece. They range from ten to thirty carats in size, and are not free from imperfections.

There are several precious stones of a green

colour that are sometimes sold as emeralds. The more important of these is chrysolite or periodot, a silicate of magnesia coloured green by iron. It is of a soft green colour. Fine examples exist in various church treasures collected probably during the Crusades, but the original locality of these gems in unknown. The common form of the mineral (olivine) is abundant in eruptive rocks. Hiddenite, a silicate of aluminium and lithium, found in North Carolina, is much esteemed in America, under the name of lithium emerald. Tourmaline, when of a dark green colour is sold as Brazilian emerald. It is, however, easily recognised by its dichroism.

Opal. Opal consists of hydrated silica. It owes its peculiar play of colour to the numerous irregular fissures traversing it, which contain laminæ that reflect the rays of different colours. The finest opals formerly came from Hungary, Mexico, and Honduras, where they occur in igneous rocks. In Hungary, the opal mines at Dubnik are mined by the State. The opal occurs lining open fissures in pyroxene-andesite. The opals are sorted into four classes. The undertaking affords employment to 140 workmen, and yields about 12,000 carats annually. In 1889 a rich vein was found, and the yield was 28,000 carats. Australia is now the chief source of production of precious opal. The rich opal fields of White Cliffs, New South Wales, was discovered by a mere accident, in 1889, and since then opal mining has become an important industry. The mineral occurs in seams in Cretaceous deposits, and varies in value from very little up to £25 an ounce, the unit of purchase in the rough. A specimen recently found, weighing 13 lbs., was a solid mass of gems. The value of the opals raised in New South Wales in 1902 was £140,000. In Queensland, the workings cover a wide district, having been traced from Eulo, in the Gunnamulla district, about 150 miles north of Bourke, in New South Wales, for some 500 miles in a north-westerly direction as far as Winton, in the county of Ayrshire. The precious opals met with occur here and there in patches in upper Cretaceous sandstones and clays. In places the mineral is found scattered over the surface, being set free by denudation, but such occurrences furnish little evidence of precious opal below. The average depth of the shafts is 14 feet, and the deepest is about 65 feet. The great difficulty in the progress of the industry is the scarcity of water, the annual output being dependent on the rainfall. The value of the Queensland production

in 1902 was £7,000. Mr. G. F. Kuntz declares that more opals are sold in a year than were sold in fifty years before the Australian mines were opened. The beauty united to the low price and abundance of much of the opal won makes it available for all kinds of decorative effects in the jeweller's art. Of precious opal, the finest, from Czerwenitza, Hungary, is in the celebrated bouquet of gems presented by the Empress Maria Theresa to her Consort. It is now in the Vienna museum. It weighs 594 grammes and is valued at £160,000. Central America and Mexico are also said to be producers, and occurrences have been noted in Tasmania. The most important point in buying opals is colour. Red is in the keenest demand, or red in combination with yellow, blue, and green. Pattern is a secondary consideration in valuing the stone. Harlequin is the rarest of all, and when the colour squares of red, yellow, blue and green are regular and distinct, its beauty is remarkable. The flash opal, though not so rare as the harlequin, is scarcely less attractive, particularly when its colour veins are of the true ruby or pigeon's blood hue.

Turquoise.-Turquoise is of a bright blue to greenish blue colour but opaque. The most valuable stones are azure blue with a resinous lustre, taking a high polish. The colour gradually fades on exposure to sunlight. The gem was appreciated even in the time of Pliny. It is a phosphate and hydrate of alumina coloured by copper. It occurs in small reniform masses in Persia and Arabia. The celebrated turquoise mines of Persia are situated in a mountainous region 6,000 feet above sea level. They employ 1,500 persons. Many of the mines are mere burrows. Turquoise mining is now active in the United States where the gem is in great favour. Turquoise has also been found in the Murchison district, Western Australia, and deposits are being worked in Egypt. Odontolite, frequently sold as an inferior turquoise, is fossil bone coloured by copper.

Garnet.-Gems of the garnet group are obtained in great abundance. The varieties most esteemed are the violet-coloured almandine or precious garnet, the brownish-red or carbuncle, usually cut en cabochon, the yellowish-brown cinnamon stone, and the pyrope or Bohemian garnet. The hilly Cretaceous district of North-East Bohemia for many years supplied the world's market with garnets, but the South African garnets, a byproduct in diamond mining, have caused the abandonment of nearly all the Bohemian

mines except the extensive open-workings at Podseditz, where the Pleistocene drift containing the garnets is nine feet or more in thickness, and lies a couple of feet below the surface. Gem garnets of great beauty have been discovered in the Cowee valley, in North Carolina, the yield in 1901 being 200,000 carats, valued at £4,000 after cutting. In the same year the United States produced 4,444 tons of garnets, for abrasive purposes, valued at £31,600.

Other Precious Stones.-Chrysoberyl is a beautiful greenish-yellow precious stone of great rarity. It is the third hardest in the series and consists of alumina and glucina. It occurs in the form of rolled pebbles in Brazil and Russia. Cut en cabochon, the less transparent specimens give one of the stones termed by jewellers "cat's eye." Zircon, hyacinth, and the green-coloured jargoon, are silicates of zirconia. They are the heaviest of all precious stones, and occur embedded in granite, basalt, and lava, and in alluvial beds in Ceylon. The topaz is a fluosilicate of aluminia, usually of a yellowishbrown colour, sometimes pale blue. The best come from Brazil. Topaz is found in veins in granite and in the form of rolled pebbles. The transparent moonstone, mined in the Kandy district of Ceylon, the apple-green amazon stone, the Norwegian sun-stone, and the iridescent labradorite, are forms of felspar owing their value as ornamental stones to certain effects of light.

Ornamental Stones.-Of the pure siliceous minerals used as ornamental stones, there are the crystalline transparent forms of silica, the pure colourless rock-crystal, the purple amethyst, the yellow citrine, the brown cairngorm, and the pink rose-quartz, together with the amorphous, translucent, or opaque forms, the white chalcedony, the red carnelian, the deep reddish-brown sard, the green chrysoprase, and the olive-green plasma. The banded variety of chalcedony is agate; when the bands of colour lie in even planes it is termed onyx; or, with alternating bands of red and white chalcedony, sardonyx. For purposes of ornament, the colour of most of these stones is frequently modified by staining, a process practised even in the time of Pliny. In moss agate, and mocha stone, the mosslike markings are due to manganese oxide. Of the opaque variety, jasper, there are several forms, ribbon jasper, with the colours in stripes, Egyptian jasper found in rolled pebbles, with the brown colours in concentric

zones, and bloodstone or heliotrope, a jasper of deep green colour, with blood-red spots. Quartz, either fibrous or with some enclosed fibrous body, constitutes a variety of cat'seye, which has a peculiar lustre. The socalled crocidolite, which first came to Europe from Cape Colony in 1870, is a fibrous form of quartz of rich brown colour. It was formerly exceedingly rare, but is now obtained in considerable quanties. In 1901, the production was 3 tons valued at £150. The brilliantly spangled aventurine is quartz with disseminated particles of mica.

Brazil is the principal source of supply of amethysts. Recently, an immense amygdaloidal cavity lined with amethyst, was found, surpassing anything of the kind previously known. It measured 33 feet in length, 16 feet in width, and 10 feet in height, and weighed about 35 tons. It was put together to form the Amethyst grotto that was one of the attractions of the Düsseldorf Exhibition of 1902.

The centre of the agate cutting industry is at Oberstein in Germany, where the river Idar in its descent to the Nahe presents a succession of falls through a distance of 24 miles and supplies power for some 60 polishing works. Precious and semi-precious stones are received for polishing from all parts of the world, and the development of the industry has necessitated the use of steam-engines and electric motors in place of the water power originally employed. The agates are ground on sandstone wheels: the workman lying horizontally presses the agate against the grindstone, obtaining purchase by pressing his feet against a block fixed to the floor. (Fig. 14). An important branch of the industry is the preparation of blanks for cutting onyx cameos in Paris and Italy. The cameos are usually cut on stones that have layers of different colours, so that the design appears in white on a red, brown, or black ground.

The finest example of sardonyx cameo is in His Majesty's collection at Windsor Castle. It measures 7 by 5 inches, and is cut upon a rich Oriental sardonyx of four strata. It is a contemporary portrait of the Emperor Claudius. The ground is in the dark brown stratum, the laurel wreath and front of the cuirass in the honey-brown, and the head and hair in the white. The whole is surrounded by a raised border enriched with moulding cut in the thickness of the stone. The most important cameo in existence is the "Gemma Augustea" (Fig. 15) in the Art Historical Museum in Vienna. It is cut upon sardonyx of two layers,

the figures being cut in the bluish-white layer, while the dark forms the background. It measures 7 by 83 inches. The design represents Tiberius before his splendid triumph, 12 B.C., descending from his chariot, with Germanicus standing at his side, to present himself to his father Augustus who is seated with the emblems of Jupiter, by the side of the godess Rome. The figures at the base represent captive Germans, and Roman soldiers erecting a trophy. The process of cameocutting, and some of the best examples, have been described by Mr. J. B. Marsh and by

In

nephrite forms narrow veins in serpentine. East Turkestan it was worked by fire-setting, and it occurs in considerable quantities in Siberia. Greyish-green jade is known in situ on Monte Viso in Italy, and in Burma. The Maoris still use nephrite for tools, the mineral having recently been discovered for the first time in situ in New Zealand, in serpentine, on D'Urville Island. Large bodies of jade-stone are found near Hsu-Yen, on the river Ta-Yang, that empties in the bay of Corea. In many localities these minerals have been found only in worked pieces. In Mexico and Central

Mr. C. Davenport. The celebrated so-called Mexican onyx, the occurrence of which has been described by Mr. W. Eassie, is in reality an aragonite stalagmite. This rich ornamental stone is largely quarried.

Jade. Under the name of jade are included two minerals, nephrite and jadeite, closely similar in appearance and properties. It was found by Damour, in 1865, that the former is a silicate of alumina, lime, and magnesia, and the latter a silicate of alumina and soda. These tough minerals are mostly found in detrital deposits. Even now but a few localities are known where they occur in situ. In Europe the only one is at Jordansmühl in Silesia, where

• Journal of the Society of Arts, vol. 35, p. 147. +Ibid, vol. 49, p. 141.

Ibid, vol. 24, p. 503.

America jadeite only is found, not nephrite whilst amongst the jades of the north-west coast of America, Siberia, and New Zealand, jadeite has not been recognised. The most remarkable specimen of jadeite known is a Mexican adze with a grotesque human figure carved on its face. It weighs 229 ozs., and is now in the New York Museum. It has been described by Mr. G. F. Kunz, who, in a recent paper, discusses the question, whence the jade so highly prized in Mexico and Central America by the primitive people was obtained. The problem is of great interest to archeolo. gists, and its solution might give to the world a beautiful ornamental stone.

Amber. Since the times of the Etruscans, the Greeks, and the Romans, amber has been obtained from East Prussia, which is still the

chief source of supply. The Prussian Government has a monopoly of the industry. The fossil resin was first found washed up by the water from a submarine bed of Tertiary age, extending along the shores of the Baltic to Cromer on the Norfolk coast. This sea amber is characterised by the fact that it has no weathered exterior. After storms, large quantities are washed ashore and collected. It is also collected in nets, and since 1869 divers have been successfully employed by the Königsberg firm of Stantien and Becker, to collect amber from the bottom of the sea and to dig it out. More than twenty large steam dredgers are in use raising the material from a depth of 7 to 11 yards. Quarries are also worked near the sea-shore, and every year

FIG. 15.

GEMMA AUGUSTEA.

a large proportion of the amber production is obtained in this way. The greyish-blue sandy clay, known as blue earth, containing the amber, is opened up by quarrying and by ordinary mining. The principal workings are about mid-way between Memel and Dantzig, the largest mine being at Palmnicken, where the blue earth is 16 feet thick. The mine galleries have a total length of 150 miles, and the annual yield of amber is about 200 tons. The amber is separated from the enclosing earth by washing on coarse screens with a powerful jet of water. The cleaned amber is finally sent to Königsberg, where it is sorted for the market into nearly a hundred different varieties. The flat pieces of amber are turned for smokers' requisites, and the round pieces cut in facets or worked into beads for bracelets and necklaces. The pieces of amber can be softened in boiling

linseed oil, and the cloudy specimens rendered clear. The small impure amber is used for the manufacture of varnish. The total annual consumption of the world of crude amber represents a value of about £150,000. Many imitations of amber are manufactured, and compressed amber, or ambroid, made by compressing small pieces at great pressure and high temperature, is largely utilised. The income derived by the Prussian Government from the amber industry amounted in 1811 to £1,100 annually, and rose in 1895 to £35,500. The mineral is State property, but, as a matter of fact, the working and sale was leased to the firm of Stantien and Becker for many years. On July 1st, 1899, the Prussian Government purchased the whole of the works of this firm, and started to mine and trade on the State account. The purchase price was £487,500. Details of the various uses of amber are given in a paper read by Mr. P. L. Simmonds.* Amber is obtained in irregular masses, usually of small size. A single enormous piece of amber, weighing nearly 7 lbs., was found a few years ago, by some fishermen at Langlutjensand. The largest piece on record, 18 lbs., is in the Berlin Museum.

Other Ornamental Stones.-Among other ornamental stones are the comparatively soft green malachite (carbonate of copper) and the azure blue lapis lazuli, a complex combination of silicate and sulphate, which was formerly powdered and washed to make the ultramarine of the artist. The richer varieties are used in mosaic, and for costly vases and jewellery. Steatite, or soap-stone, is used by the Chinese for carving figures. Jet, a variety of lignite, the Gagates of the ancients, is largely used for mourning ornaments. In England, jet mining is not pursued as a regular occupation, in the cliffs near Whitby a little burrowing is done in stormy weather when agricultural work is difficult. The manufacture of Whitby jet was described in 1873 by Mr. J. A. Bower.† late years the trade has died out. Comprehensive descriptions of the different precious and ornamental stones will be found in Mr. G. F. Kunz's well-known work on the precious stones of the United States, and in Professor Max Bauer's "Edelsteinkunde," of which an English translation by Mr. L. J. Spencer is announced.

Of

The Rare Earths.-In the early days of chemistry the term "earth" was applied to certain substances now known to be oxides of • Journal of the Society of Arts, vol. 18, p. 185. + Ibid., vol. 22, p. 80.