Part 4

In a powdered state this substance has long been used by the artists of India and China for the cutting and polishing of precious stones, and even of the diamond; but, though it will in some degree operate upon that gem, it is not sufficiently hard to bring out the peculiar beauty of it in a degree at all comparable to that which is effected by the European lapidaries with diamond powder. The Chinese also use adamantine spar for polishing steel, and in the composition of the finer kinds of porcelain or earthenware. For the cutting of seals and precious stones European workmen consider it preferable to emery; but, for minute engraving, it is much inferior to diamond powder.

60. _CHRYSOBERYL is a gem of yellowish or brownish green colour, harder than quartz (76), and sometimes transparent; but often only semi─transparent, in which case it exhibits a bluish light, floating in the interior of the stone._

_It is usually found in rounded pieces, but is sometimes crystallized in compressed six─sided prisms, and in double six─sided pyramids._

So little is this gem in request in Europe, that it is seldom to be found in the possession of jewellers; but in Brazil it is considered inferior only to the diamond. It is usually procured from South America; yet it occurs in Saxony; and, with the ruby and sapphire, amongst sand in the rivers of Ceylon.

Such is the hardness of the chrysoberyl, that, when properly polished, which is a difficult operation, it is capable of receiving a lustre nearly equal to that of the diamond. We are informed that, a few years ago, a considerable number of these gems were imported into this country from Brazil, but that the greater part of them were entirely spoiled by inferior workmen, and that the rest were so ill─cut that they remained unnoticed, and without value. The smaller stones are said to appear to most advantage in circular ear─drops; and the larger specimens form necklaces and ring stones of great beauty.

The variety which exhibits an opalescent appearance, or presents a bluish light, undulating as it were in the interior of the stone, and changing its situation according to the position of the observer, is chiefly valuable as an article of curiosity: the transparent kind is always preferred by the jeweller.

SCHORL FAMILY.

61. _The TOPAZ is a gem usually of a wine─yellow colour, but sometimes orange, pink, blue, and even colourless, like rock_ _crystal; of a lamellar or foliated structure, harder than quartz, but not so hard as ruby._

_It varies considerably in its crystallization; is 3½ times heavier than water; and, when placed upon any object, shows a double image of it._

The name of topaz is derived from an island in the Red Sea, where the ancients found a stone, but very different from ours, which they denominated topaz. The best topazes are of a deep colour, and are imported from Brazil; the most brilliant ones are supposed to be those of Saxony; but the latter are generally of very pale colour. This species of gem is found in many parts of Europe, but defective in transparency, and sometimes even opaque. It occurs in large crystals, and rolled masses, in an alluvial soil (269), in the upper parts of Aberdeenshire, Scotland; and in veins, along with tin─stone, at St. Anne’s, in Cornwall. Topazes, more than a pound in weight, have been found in Scotland.

Mr. Mawe speaks of a topaz mine at Capon, near Villa Rica, in Brazil. In two breaks or slips of the rocks, he says, there were little soft places where the negroes found the topazes by scraping in them with pieces of iron. He himself observed at least a cart─load of inferior topazes, any number of which he might have taken away; but all that he saw were defective and full of flaws.

These stones vary much in size; some, particularly those of Siberia, being extremely small, and others being upwards of an inch in thickness. In the Collection of Natural History at Paris there is a Brazilian topaz which weighs four ounces and a quarter. These stones are not sufficiently scarce to be, in general, much valued by the jeweller or lapidary. The deep yellow variety is preferred to the pale sort, although the latter is often superior to it both in size and hardness.

Figures have sometimes been engraved on the topaz; and these, when well executed, are of great value. In the National Museum at Paris there is a superb Indian Bacchus engraven on a topaz. The cabinet of the Emperor of Russia contains several fine topazes of this description.

Some of the coarse kinds of topaz are broken down, pounded, and used instead of emery for the cutting of hard minerals; and powdered topaz was formerly kept in apothecaries’ shops, and sold as an antidote against madness.

It is a somewhat singular circumstance, that, if the Saxon topaz be gradually exposed to a strong heat in a crucible, it will become white and, on the contrary, that Brazilian topazes by the same process become red or pink. By exposure to a still stronger heat, the Brazilian topaz changes its colour to a violet─blue.

Jewellers usually divide topazes into the following kinds:

62. BRAZILIAN and SAXON, already mentioned.

63. BOHEMIAN.—These are found chiefly in the tin mines of Bohemia, are of small size, deficient in transparency, have only grey or muddy white colours, and are of little value.

64. BLUE TOPAZ.—This is a large Brazilian gem, which varies in size from one or two carats to two or three ounces. A fine blue topaz, without flaw, and which weighed an ounce and a quarter, was sold for 200 guineas. It is sometimes difficult to distinguish a blue topaz from an aqua marine (68).

65. PINK TOPAZ.—Some beautiful rose─coloured varieties of topaz have been brought from Asia Minor, and others are found in South America; but the pink topazes in the jewellers’ shops are chiefly stones of the yellow Brazilian kind, which have had their colour changed by heat.

66. The WHITE, or NOVA MINA TOPAZ, is a perfectly colourless and transparent variety. It generally occurs of small size, and is in considerable estimation in Brazil for ear─rings, or for being set round yellow topazes. Small stones of this description have recently been found at St. Michael’s Mount, in Cornwall.

There is imported from Brazil a yellow kind of crystal (83), which is so similar, in its appearance, to the yellow topaz as sometimes to be imposed upon purchasers for that stone.

67. _The EMERALD is a well─known gem, of pure green colour, and somewhat harder than quartz._

_Its natural form is a short six─sided prism; but it is sometimes found massive, and rounded like a pebble._

By the ancients the emerald was a gem much in request, and particularly for engraving upon. They denominated it _smaragdus_, and are said to have procured it from Ethiopia and Egypt; but, besides the true emerald, Pliny, under this title, includes green jasper (96), malachite (231), fluor spar (194), and some other green minerals. The pillars of emerald in the temple of Hercules at Tyre, mentioned by Herodotus, and the large emeralds described by Pliny as having been cut into columns and statues, cannot be referred to the true emerald.

The deepest coloured and most valuable emeralds that we are acquainted with are brought from Peru. They are found in clefts and veins of granite, and other primitive rocks; sometimes grouped with the crystals of quartz (76), felspar (110), and mica (123); and, not unfrequently, loose in the sand of rivers. The most ancient emerald mine is that of Manta, in Peru, but it has been some time exhausted; and most of the emeralds that are now brought to Europe are obtained from a mine situated in the valley of Tunca, between the mountains of New Grenada and Popayan.

The emerald is one of the softest of the precious stones; and is almost exclusively indebted for its value to its charming colour. The brilliant purple of the ruby, the golden yellow of the topaz, the celestial blue of the sapphire, are all pleasing tints; but the green of the emerald is so lovely, that the eye, after glancing over all the others, finds delight in resting upon this. In value it is rated next to the ruby; and, when of good colour, is set without foil and upon a black ground, like a brilliant diamond. Emeralds of inferior lustre are generally set upon a green gold foil. These gems appear to greatest advantage when table cut (Pl. II, Fig. 9), and surrounded by brilliants, the lustre of which forms an agreeable contrast with the quiet hue of the emerald. They are sometimes formed into pear─shaped ear─drops; but the most valuable stones are generally set in rings. A favourite mode of setting emeralds among the opulent inhabitants of South America is to make them up into clusters of artificial flowers on gold stems.

The largest emerald that has been mentioned is one said to have been possessed by the inhabitants of the valley of Manta, in Peru, at the time when the Spaniards first arrived there. It is recorded to have been as big as an ostrich’s egg, and to have been worshipped by the Peruvians, under the name of the Goddess, or Mother of Emeralds. They brought smaller ones as offerings to it, which the priests distinguished by the appellation of daughters. Many fine emeralds are stated to have formerly been bequeathed to different monasteries on the Continent; but most of them are said to have been sold by the monks, and to have had their place supplied by coloured glass imitations. These stones are seldom seen of large size, and at the same time entirely free from flaws.

The emerald, if heated to a certain degree, assumes a blue colour; but it recovers its proper tint when cold. When the heat is carried much beyond this, it melts into an opaque coloured mass.

The precious stone called oriental emerald (56) is a green and very scarce variety of the oriental ruby.

68. _The BERYL, or AQUA MARINE, is a light or mountain green variety of the emerald, sometimes straw─coloured, bluish, yellow, or even white._

These stones are of such frequent occurrence, even in large pieces perfectly clear and free from flaws, they are in general so soft, and have so little the brilliancy of other gems, that they are usually considered of inferior value. The most beautiful kinds are brought from Dauria, on the frontiers of China, from Siberia, and from Brazil. They are also found in Saxony and the South of France, and are very common at Baltimore, in North America. Specimens of aqua marine have been obtained from the upper parts of Aberdeenshire, Scotland, where they sometimes occur in alluvial soil, along with rock crystal and topaz. These stones have also been found, embedded in granite, near Lough Bray, and Cronebane, in the County of Wicklow, Ireland; and also in mountain rock, in some parts of Devonshire.

They are cut by means of emery (58), and polished with tripoli (119). The darkest green specimens are set upon a somewhat steel─coloured foil; and the pale ones are either placed, like the diamond, on a black ground, or upon a silvery foil. The aqua marine is usually made into necklaces; but it is likewise employed for brooches, and not unfrequently for steel stones and intaglios. The larger ones are in much esteem among the Turks for the handles of stilettos.

69. _The TOURMALINE is a stone belonging to the same family as the emerald, and generally of a smoky blackish colour: sometimes, however, it is green, red, blue, or brown; and, when not very thick, it is transparent._

_It is occasionally found in shapeless masses, but more frequently crystallized in three, six, or nine─sided prisms, variously truncated or terminated; and its weight is somewhat more than three times that of water._

This stone was first made known in Europe, about the beginning of the last century, by the Dutch merchants, who brought it from the island of Ceylon, where it is principally found. When strongly heated it becomes electric; one of the summits of the crystal negatively, and the other positively. An early writer, by whom it is mentioned, says, that “it has the property not only of attracting ashes from the warm or burning coals, but that it also repels them again, which is very amusing: for as soon as a small quantity of ashes leaps upon it, and appears as if endeavouring to writhe themselves by force into the stone, they in a little time spring from it again, as if about to make a new attempt. It was on this account that the Dutch called it the ashes drawer.”

Since the above period, tourmaline has been found in Brazil; and in Norway, Germany, France, and several other parts of Europe. It generally occurs embedded in different kinds of mountain rock; and, in these, is rather confined to single beds or strata, than disseminated through the whole mass of the mountain. A piece of tourmaline, of cylindrical form, and brownish grey colour, was some time ago discovered in the neighbourhood of Kitt─hill, near Callington, Cornwall. Black tourmaline, both in large and small crystals, is found in granite rock, in the vicinity of the Logan, or Rocking─stones, near Treryn, in the same county.

When laid on a table, the tourmaline appears a dark and opaque stone; but, when held against the light, it has generally a pale brownish hue. It is sometimes cut, polished, and worn as a gem; but, on account of the muddiness of its colours, it is not in general much esteemed. Those persons who wear tourmalines set in rings consider them more as objects of curiosity than of elegance: they show them as small electrical instruments, which, after being heated a little while by the fire, will attract and repel light bodies.

In the superb collection of minerals of the British Museum, there is a magnificent specimen of _red tourmaline_, or _rubellite_, which has been valued at 1000_l._ sterling. It was presented by the King of Ava to the late Colonel Symes, when on an embassy to that country, and was afterwards deposited by the latter in Mr. Greville’s collection; with that collection it became the property of the British Museum.

GARNET FAMILY.

70. _The PRECIOUS, or NOBLE GARNET, is a gem of crimson colour, which, when crystallized, has the form of a twelve─sided solid (Pl II, Fig. 11, 12). It is sufficiently hard to scratch quartz, and is about four times as heavy as water._

This stone is found abundantly in many mountains (particularly of primitive rock), in different parts of the world. But garnets of the hardest and best quality are brought from Bohemia, where there are regular mines of them; and a great number of persons are there employed in collecting, cutting, and boring them. The boring is performed by an instrument having a diamond at its extremity, which is rapidly turned by a bow. The work is so expeditiously performed, that an expert artist can bore 150 garnets, or he can cut and polish thirty, in a day. In Suabia there are two towns in which upwards of 140 persons are employed in these operations.

In general garnets are stones of inferior value. When compared with the ruby, those even of finest quality have a very sombre appearance. The kinds most esteemed are such as have a clear and intense red colour, or a rich violet or purplish tinge. The best garnets are cut in the manner of other precious stones, and are usually set upon a foil of the same colour. To heighten the colour and transparency of certain garnets, jewellers either form them into what are called doublets, by attaching to the lower part of the stone a thin plate of silver, or they hollow them underneath.

Crystals of garnet sometimes occur three or four inches in diameter. These are cut into small vases; which, if of good colour, and free from defects, are highly valued. Many fine engravings have been executed on garnet. One of the most beautiful that is known is a figure of the dog Sirius, in the possession of Lord Duncannon.

The coarser kinds of garnet are used as emery for the polishing of other minerals; and are thus prepared. They are made red─hot, then quenched in water, reduced to powder in an iron mortar, and lastly diffused through water, poured into other vessels, and allowed to settle, in order to obtain an uniform powder. This powder is known to artists by the name of _red emery_.

It has been conjectured that our garnet was the same kind of stone which, on account of its colour, the ancients denominated _carbuncle_.

71. COMMON GARNET.—A very inferior variety of garnet, of brown or greenish brown colour, is found in our own country, and particularly amongst rocks near Huntley, in Aberdeenshire, Scotland. These garnets, however, are, in general, so soft as to be of little value to the lapidary; and consequently are seldom cut or polished for ornamental purposes. But being easily fused, and abounding in iron, they are occasionally employed as a flux in the smelting of rich iron ores: and as an addition to poor ones.

72. SYRIAN GARNETS _are distinguished by their violet or purplish tinge_. Some writers state that they have their name from the word Soranus, which signifies a red stone; and others from Sirian, a town in Pegu, where they are said to be found in great beauty.

73. PYROP GARNETS _are of a dark blood─red colour_, which, when the stones are held between the eye and the light, falls strongly into yellow: they are chiefly brought from Bohemia: are employed in almost every kind of jewellery, and generally set with a gold foil. At Waldkirch, in Suabia, there are twenty─four mills for the cutting and polishing of pyrop garnets: and 140 masters are occupied in manufacturing these stones.

74. VESUVIAN _is a liver─brown kind of garnet_, that was originally found among rocks ejected from Mount Vesuvius; and in the vicinity of which mountain it still occurs in considerable abundance. At Naples it is cut into stones for rings and other ornaments. Vesuvian has of late years been found in other parts of Europe; and even at Kilranelagh, and Donegal, in Ireland.

75. CINNAMON STONE _is a kind of garnet of hyacinth─red colour_, which is found in angular and roundish pieces among the sand of rivers in the island of Ceylon. It is cut as a precious stone; and, when of good colour, and free from flaws, is of considerable value.

QUARTZ FAMILY.

76. _COMMON QUARTZ is a hard and foliated substance, usually of white or grey colour, and more or less transparent._

_It is generally found in shapeless masses, which are nearly thrice as heavy as water, and the fracture of which is glassy. When crystallized, it most commonly has the form of a six─sided prism, terminated by a pyramid of six sides._

This kind of stone forms a constituent part of many mountains, and is very common in our own, as well as in most other countries. It is sufficiently hard to scratch iron and steel; and it has the property, after having been several times successively made red─hot, and dipped into water, of communicating to that fluid a certain degree of acidity.

Quartz is employed, in place of sand, for making the finer kinds of glass; and also in the manufacture of porcelain. For the latter purpose great quantities are collected from the mountains of Wales, ground into powder, and in that state shipped to Liverpool, and other parts. After having been burnt and reduced to powder, it is sometimes mixed with clay, and formed into bricks for the construction of glass furnaces: these are capable of resisting the intense heat which is requisite in the fusion of glass.

77. BURRSTONE _is a vesicular and corroded variety of quartz, which forms a most excellent and valuable_ _kind of millstone_. It is chiefly found in France; but is so much esteemed by the English millers, that the Society of Arts, in London, for many successive years, offered a considerable reward for its discovery in Great Britain. At length a vein of burrstone was discovered in the Moel y Golfa hills, North Wales, by a Mr. Evans, who, in consequence received a premium from the Society. About the same time another vein was opened near Conway; and the same Society, in 1800, gave a premium of 100_l._ to the widow and orphan children of the discoverer. Both these quarries were sufficiently convenient for water carriage; yet the demand for the Cambrian burr did not answer the expectation, and millstones of French production were still preferred to them.

The mode of splitting these stones, as it is practised in some parts of France, is singular, and affords a proof of the extraordinary power of capillary attraction. The blocks are first cut into the form of cylinders, sometimes many feet in height. To split these horizontally into millstones, circular indentations are made round them, at proper distances, according to the thickness that is to be given to the stones; wedges of willow, that have been dried in an oven, are then driven into the indentations with a mallet. When these have been sunk to a proper depth, they are moistened with water; and, after a few hours, the several stones that have been marked out are found to be perfectly separated.

78. _ROCK CRYSTAL is an extremely beautiful kind of quartz, sometimes perfectly transparent, and sometimes shaded with grey, yellow, green, brown, or red. It occurs in the form of crystals with six sides, each terminated by a six─sided prism._

The name of this substance was considered by the ancients to signify ice, or water crystallized; and they imagined that crystal was produced from a congelation of water.

Its uses are numerous. It is cut into vases, lustres, and snuff─boxes; and many kinds of toys of extremely beautiful appearance are made of it. When pure and perfectly transparent, it is much in request by opticians, who make of it those glasses for spectacles which are called _pebbles_, and who use it for various kinds of optical instruments. The best crystal is imported from Brazil and Madagascar, in blocks, not unfrequently from fifty to a hundred pounds in weight.

This stone is wrought into the different shapes that are required, by sawing, splitting, and grinding. The sawing is effected by an extended copper wire fixed to a bow: the wire is coated with a mixture of oil and emery, and is drawn backward and forward until the operation is performed. But, as this process is a tedious one, particularly when the mass is large, a more expeditious, although less certain, method is sometimes adopted. The crystal is heated red hot, and a wet cord is drawn across, in the direction that the workman intends to split it. By the rapid cooling thus effected, in the direction of the cord, the stone easily splits by a single blow of the hammer, and generally in the direction required. The grinding is performed by means of emery: and the polishing effected by tin ashes and tripoli.

The ancients held vases that were made of this stone in great estimation, particularly when they were of large size. Of two cups which the tyrant Nero broke into pieces in a fit of despair, when informed of the revolt that caused his destruction, one was estimated to be worth more than 600_l._ of our money. The most valuable kind of crystal that was known to the ancients was obtained from the island of Cyprus; but it was often faulty in particular parts, having flaws, cracks, and blemishes. When the crystal was used for the engraving of intaglios and cameos, the artist could sometimes conceal these defects amongst the strokes of his work; but, when it was to be formed into cups or vases, this could not be done, and for the latter purpose the purest pieces only could be employed.

In the counties of Cornwall and Derby, in the neighbourhood of Bristol, and amongst the mountains of North Wales, small crystals of this kind are frequently found: these are respectively called _Cornish_, _Buxton_, _Bristol_, and _Snowdon_ diamonds. We are informed that the crevices of some parts of Mont Blanc and the Alps contain rock crystal in such abundance as to be perfectly bristled with it.