be produced on the spot where it is discovered, or have been transported from the place of its origin, has not been ascertained. It is found also in veins filled with soil of a similar nature. We shall here add a short hisory of the diamond mines.

The diamond mines are found only in the kingdoms of Golconda, Visapour, Bengal, the island of Borneo, and Brasil. There are four or five mines, or rather three mines and two rivers, whence diamonds are obtained. The mines are, 1. That of Raolconda, in the province of Carnatica, five days journey from Golconda, and eight from Visapour. It has been discovered about 200 years. 2. That of Gani, or Coulour, seven days journey from Golconda eastward. It was discovered 150 years ago by a peasant, who digging in the ground found a natural fragment of 25 carats. 3. That of Soumelpour, a large town in the kingdom of Bengal, near the Diamond-mine. This is the most ancient of all: it should rather be called that of Goual, which is the name of the river, in the sand whereof these stones are found. 4. The fourth mine, or rather the second river, is that of Succudan, in the island of Borneo; and, 5. That of Serro-do-Frio in Brasil.

Diamond-mine of Raolconda.-In the neighbourhood of this mine the earth is sandy, and full of rocks and copse-wood. In these rocks are found several little veins of half and sometimes a whole inch broad, out of which the miners, with a kind of hooked irons, draw the sand or earth wherein the diamonds are; breaking the rocks when the vein terminates, that the track may be found again, and continued. When a sufficient quantity of earth or sand is drawn forth, they wash it two or three times, to separate the stones. The miners work quite naked, except a thin linen cloth before them; and besides this precaution, have likewise inspectors, to prevent their concealing diamonds, which, however, they frequently find means to do, by watching opportunities when they are not observed, and swallowing them.

Diamond-mine of Gani or Coulour.-In this mine are found a great number of diamonds from 10 to 40 carats, and even more. It was here that the famous diamond of the Great Mogul, which before it was cut weighed 793 carats, was found. The diamonds of this mine are not very clear: their water is usually tinged with the quality of the soil; being black where that is marshy, red where it partakes of red, sometimes green and yellow, if the ground happen to be of those colours. Another defect of some consequence is a kind of greasiness appearing on the diamond, when cut, which takes off part of its lustre.-There are usually no less than 60,000 persons employed in this mine.

When the miners have found a place where they intend to dig, they level another somewhat bigger in the neighbourhood thereof, and inclose it with walls about two feet high, only leaving apertures from space to space, to give passage to the water. After a few su

perstitious ceremonies, and a kind of feast which the master of the mine makes for the workmen, to encourage them, every one goes to his business, the men digging the earth in the place first discovered, and the women and children carrying it off into the other walled round. They dig a few feet deep, and till such time as they find water. Then they cease digging; and the water thus found serves to wash the

earth two or three times, after which it is let out at Diamond an aperture reserved for that end. This earth being genus. well washed, and well dried, they sift it in a kind of open sieve, and lastly, search it well with the hands to find the diamonds. This mine is in a plain of about one league and a half in extent, bounded on one side by a river, and on the other by a range of lofty mountains, which form a semicircle. It is said that the nearer the digging is carried to the mountains, the diamonds are the larger.

Diamond-mine of Soumelpour, or river Goual.Soumelpour is a considerable town near the river Goual, which runs into the Ganges. It is from this river that all our fine diamond points, or sparks, called natural sparks, are brought. They never begin to seek for diamonds in this river till after the great rains are over, that is, after the month of December; and they usually even wait till the water is grown clear, which is not before January. The season at hand, eight or ten thousand persons, of all ages and sexes, come out of Soumelpour and the neighbouring villages. The most experienced among them search and examine the sand of the river, and particularly where it is mixed with pyrites, going from Soumel pour to the very mountain whence it springs. When all the sand of the river, which at that time is very low, has been well examined, they proceed to take up that wherein they judge diamonds likely to be found; which is done after the following manner: They dam the place round with stones, earth, and fascines, and throwing out the water, dig about two feet deep: the sand thus got is carried into a place walled round on the bank of the river. The rest is performed after the same manner as at other mines.

Diamond-mine in the island of Borneo, or river of Succudan.-We are but little acquainted with this mine; strangers being prohibited from having access to it: though very fine diamonds have been brought to Batavia by stealth. They were formerly imagined to be softer than those of the other mines; but experience shows they are in no respect inferior.

Diamond-mine of Serro-do-Frio.-A description of this mine was given by D'Andrada in 1792, to the Natural History Society of Paris. The mine is situated to the north of Villa Rica, in the 18th degree of south latitude. The whole country in which the diamonds are found abounds with ores of iron; and the stratum of soil, immediately under the vegetable soil, contains diamonds disseminated in it, and attached to a gaugue or matrix which is more or less ferruginous; but they are never found in veins.

When this mine was first discovered, the searching for diamonds was so successful, that the Portuguese fleet which arrived from Rio de Janeiro in 1730 brought no less than 1146 ounces of diamonds. This unusual quantity introduced into the market immediately reduced the price; and to prevent this circumstance recurring, the Portuguese government determined to limit the number of men employed in the mines.

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As the diamond is the hardest of all substances, it Method of can only be cut and polished by itself. To bring it cutting and to that perfection which augments its price so consi- polishing derably, the lapidaries begin by rubbing several against diamonds. each other, while rough; after having first glued them to the ends of two wooden blocks, thick enough to be

held

Diamond held in the hand. It is this powder thus rubbed off the stones, and received in a little box for the purpose, that serves to grind and polish them.

genus.

17

Of estimating.

18

Celebrated

Diamonds are cut and polished by means of a mill, which turns a wheel of soft iron sprinkled over with diamond-dust mixed with oil of olives. The same

dust, well ground, and diluted with water and vinegar, is used in the sawing of diamonds; which is performed with an iron or brass wire, as fine as a hair. Sometimes, in lieu of sawing the diamonds, they cleave them, especially if there be any large shivers in them.

The method of cutting and polishing the diamond was not discovered till the 15th century. The diamonds which were employed as ornaments before that period, were in their rough and natural state. The invention is ascribed to Louis Berguen, a native of Bruges, who in the year 1476, cut the fine diamond of Charles the Bald, duke of Burgundy, which he lost the same year at the battle of Morat. This diamond was then sold for a crown, but afterwards came into the possession of the duke of Florence.

The first water in diamonds means the greatest purity and perfection of their complexion, which ought to be that of the purest water. When diamonds fall short of this perfection, they are said to be of the second or third water, &c. till the stone may be properly called a coloured one.

The value of diamonds is estimated by Mr Jefferies by the following rule. He first supposes the value of a rough diamond to be settled at 21. per carat, at a medium; then to find the value of diamonds of greater weights, multiply the square of their weight by 2, and the product is the value required. E. g. to find the value of a rough diamond of two carats : 2X 24, the square of the weight; which, multiplied by two, gives 81. the true value of a rough diamond of two carats. For finding the value of manufactured diamonds, he supposes half their weight to be lost in manufacturing them; and therefore, to find their value, we must multiply the square of double their weight by 2, which will give their true value in pounds. Thus, to find the value of a wrought diamond weighing two carats; we first find the square of double the weight, viz. 4×4=16; then 16×2=32. So that the true value of a wrought diamond of two carats is 321. On these principles Mr Jefferies has constructed tables of the price of diamonds from 1 to 100 carats.

The greatest diamond ever known in the world is diamonds. one belonging to the king of Portugal, which was found in Brasil. It is still uncut: and Mr Magellan informs us, that it was of a larger size; but a piece was cleaved or broken off by the ignorant countryman, who chanced to find this great gem, and tried its hardness by the stroke of a large hammer upon the anvil.

This prodigious diamond weighs 1680 carats and although it is uncut, Mr Romé de l'Isle says, that it is valued at 224 millions sterling; which gives the estimation of 79,36 or about 80 pounds sterling for each carat: viz. for the multiplicand of the square of its whole weight. But even in ease of any error of the press in this valuation, if we employ the general rule above mentioned, this great gem must be worth at least 5,644,800 pounds sterling, which are the product of 1680 by two pounds, viz. much above five millions

and a half sterling. But this gem is supposed by some Classifica to be a white topaz.

The famous diamond which adorns the sceptre of' the empress of Russia under the eagle at the top of it weighs 779 carats, and is worth at least 4,854,728 pounds sterling, although it hardly cost 135,417 guineas. This diamond was one of the eyes of a Mala barian idol, named Scharingham. A French grenadier, who had deserted from the Indian service, contrived so well as to become one of the priests of that idol, from which he had the opportunity to steal its eye: he run away to the English at Trichinopoly, and thence to Madras. A ship-captain bought it for twenty thousand rupees: afterwards a Jew gave seventeen or eighteen thousand pounds sterling for it at last a Greek merchant named Gregory Suffras, offered it to sale at Amsterdam in the year 1766 and Prince Orloff made this acquisition for his sovereign the empress of Russia. This diamond is of a flattened oval form and of the size of a pigeon's egg.

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The diamond of the Great Mogul is cut in rose ; weighs 279 carats, and it is worth 380,000 guineas. This diamond has a small flaw underneath near the bottom and Tavernier, page 389, who examined it, valued the carat at 150 French livres. Before this diamond was cut, it weighed 7934 carats, according to Romé de l'Isle but Tavernier, page 339, of his second volume, says that it weighed 900 carats before it was cut. If this be the very same diamond, its loss by being cut was very extraordinary.

Another diamond of the king of Portugal, which weighs 215 carats, is extremely fine, and is worth at least 369,800 guineas.

The diamond of the graud duke of Tuscany, now of the emperor of Germany, weighs 139 carats; and is worth at least 109,520 guineas. Tavernier says, that this diamond has a little hue of a citron colour; and be valued it at 135 livres tournoises the carat. Robert de Berquen says, that this diamond was cut into two that the grand Turk had another of the same size and that there were at Bisnagar two large diamonds, one of 250 and another of 140 carats.

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The diamond of the late king of France, called the Pitt or Regent, weighs 1364 carats: this gem is worth at least 208,333 guineas, although it did not cost above the half of this sum. Patrin says, that it is believed to be at Berlin, (I. 226.) and we may add, that it has probably been carried back to France among other spoils.

The other diamond of the same monarch, called the Sancy, weighs 55 carats; it cost 25,000 guineas: and Mr Duten says, that it is worth much above that price.

Brilliant DIAMOND, is that cut in faces both at top and bottom; and whose table, or principal face at top, is flat. To make a complete square brilliant, if the rough diamond be not found of a square figure, it must be made so; and if the work is perfectly executed, the length of the axis will be equal to the side of the square base of the pyramid.-Jewellers then form the table and collet by dividing the block, or length of the axis, into 18 parts. They take from the upper part, and

from the lower. This gives a plane at distance from the girdle for the table; and a smaller plane at distance from the collet; the breadth of which will

be

tion

lassifica- be of the breadth of the table. In this state the stone tion. is said to be a complete square table diamond.-The brilliant is an improvement on the table-diamond, and was introduced within the 17th century according to Mr Jefferies.

II. GENUS. ZIRCON.

I. Species. ZIRCON.

Jargon, Kirw. I. 257. Zircon, Haüy. II. 465. Id. Brochant, I. 159.

Essen. Char.-Its specific gravity about 4.4; the joints natural, some of which are parallel, and others are oblique to the axis of the crystals.

Exter. Char-Colours reddish and yellowish, greenish, greenish yellow, and whitish. The colour in general varies from green to gray, and is most commonly pale; and the polished stone exhibits in some degree the play of colours of the diamond.

It is found in rounded, angular, or flattened grains, or in small angular fragments with notched edges, and also crystallized. The primitive form is an octahedron with isosceles triangles, and the integrant molecule is an irregular tetrahedron. The following are the most common forms of its crystals.

1. A prism with four rectangular faces, each base of which has a pyramid with four faces placed on the four lateral faces, which terminates sometimes in a line, but most frequently in a point.

2. The preceding crystal, in which the opposite lateral edges of the prism are truncated.

3. The crystal (1.) in which the edges of the faces of the pyramid are bevelled.

4. The crystal (1.) having the lateral edges of the prism, and the summit of the pyramid trun

cated.

5. The crystal (1.) in which the angles between the prism and the pyramid are bevelled.

6. A prism with four faces, having the two opposite narrow, and the two others broad.

7. A double pyramid with four faces, with the edges of the common base truncated.

8. The perfect octahedron with obtuse angles. The crystals are commonly small; the surface smooth, but that of the angular fragments is rough. Lustre, 3 and 4; internal lustre 4 and 3; somewhat vitreous, or approaching to that of the diamond. Fracture imperfect or flat conchoidal; fragments, 3. Transparency, 4, 3. Causes double refraction. Hardness, 9; brittle. Spec. grav. 4.416 to 4-4700.

Chem. Char.-Infusible by the blow-pipe without addition, but with borax it forms a transparent colourless glass. The following are its constituent parts.

2. The same slightly truncated on its edges. 3. The double pyramid with four faces, or a very obtuse octahedron, which is a rare variety.

4. A prism with six faces, each base of which is terminated by an acumination with three faces, placed alternately on the three lateral edges, forming the rhom boidal dodecahedron.

The crystals are commonly small, the surface smooth;. external lustre, 3, 4; internal, 4; greasy, fracture straight foliated; cleavage double, rectangular; fragments, 3; transparency, 4, 2; causes double refraction; hard and brittle; unctuous to the touch when cut; spec. grav. 4.385 to 4.620.

Chem. Char-By the action of the blow-pipe the hyacinth loses its colour, but retains its transparency. It is infusible without borax, which converts it into a transparent colourless glass.

Localities. It is found in Ceylon in similar situations with the former; in Brazil, Bohemia, and in the rivulet Expailly, in Velay in France; and also in the neighbourhood of Pisa in Italy.

Uses. As it is susceptible of a fine polish, the hyacinth has been ranked among precious stones.

Remarks.-The analogy between the crystalline forms of the zircon and hyacinth; their double refraction; the similarity of their other characters, and particularly the results of chemical analysis, bave led Hauy to form them into one species.

A variety, under the name of cinnamon stone, has been considered as a distinct species; but the differences are so very slight, that it may be included in the description of the preceding.

III. GENUS. SILICEOUS.

1. Species. CHRYSOBERYL.

Id. Emm. Wid. Lenz. Kirw. Chrysopale, Lam. Cymophane, Hauy.

Exter. Char.-The colour is an asparagus green;

passing

Siliceous passing sometimes to a greenish white, and sometimes to an olive green; sometimes bright brown and yellowish brown, passing to yellowish gray; affords a feeble change of colour from bluish to milky white.

genus.

It is found in angular or rounded grains, which appear to have been water worn; and in crystals, exhibiting, 1. A table with six faces, elongated, of various thickness, truncated on the terminal edges. 2. A prism with four rectangular faces. 3. A prism with six faces, of which four are broader and two are narrower opposite to each other.

The grains are slightly rough, and have a considerable external lustre. The crystals are striated length wise on their lateral faces; the other faces are smooth; lustre external very shining-internal the same, intermediate between that of the diamond and the vitreous lustre.

The fracture is in all directions perfectly conchoidal; the fragments are indeterminate with sharp edges. It has little transparency, but a considerable degree of hardness. Spec. grav. 3.698 to 3.719 Wern. 3.710 Klap. 3.796 Hauy.

Chem. Char.-It is infusible without addition by the action of the blow-pipe. By Klaproth's analysis, the following are its constituent parts.

3. In another variety the summit of the pyramid is Classificatruncated by a convex cylindrical plane, the convexity tion. of which passes from one of the small opposite lateral planes towards the other.

4. In some instances the crystals are so small, that the same lateral faces almost entirely disappear, while the two larger assume a curved form, giving such crystals a tabular appearance.

The external surface of the angular fragments and of the rounded crystals is scaly, which affords an essential character to this mineral. The small lateral planes are smooth, the broad ones are distinctly striated lengthwise. Externally the surface is shining; internally shining and vitreous.

The fracture in all directions is perfectly conchoidal; the form of the fragments is indeterminate, with very sharp edges. It is almost always transparent, and refracts double; it is not so hard as quartz. Brittle. Spec. grav. 3.340 to 3.420 Wern. 3.428 Hauy. Chem. Char-By the action of the blow-pipe it is fused with borax without effervescence, and affords a greenish, transparent glass.

Id. Emm. Wid. Lenz. Mus. Lesk. Kirw. Peridot, Daub. Hauy.

Exter. Char. The most common colour is a bright pistachio green, passing to an olive green; sometimes of a bright asparagus or clear meadow green; rarely the green approaches to brown and almost to a cherry

red.

It is found in angular fragments with the edges a little notched, or in rounded grains, or in crystals having the angles and edges a little notched. The forms of its crystals are, 1. A large rectangular prism having its lateral edges truncated and sometimes bevelled, and terminated by a six-sided prism, of which two opposite sides are placed on the small lateral faces of the prism. The four others on the lateral truncated faces, the latter forming a more acute angle than the two for

mer.

2. The next form varies from the preceding, in having two additional terminating faces, placed on the broad faces of the prism, each of which is consequently situated between two of the planes corresponding to the truncated planes.

100 Klap. 100.5 Vauq. 100 Vauq.

Localities, &c. This mineral is brought from the Levant, but it is not known whether it is found in Asia or Africa. It has been discovered in Bohemia; and crystallised specimens included in a kind of lava have been brought from the isle of Bourbon. As it is usually found in rounded fragments, in the midst of earthy substances, its relative situation is scarcely known.

Uses. The chrysolite has been often employed for various purposes as a precious stone, but as it possesses no great degree of hardness, it is not much esteemed.

Substances of a very different nature have been, at different times, described under the name of Chrysolite. It appears that the yellow chrysolite of the ancients is the same with our topaz, and that their green topaz is our chrysolite. Plin. lib. xxxvii. cap. 8.

3. Species. OLIVINE.

Id. Emm. Wid. Lenz. Kirw. Lameth. Chrysolite en grains irreguliers, De Born. Peridot Granuliforme, Hauy. Chrysolith des Volcans, of many mineralogists.

Exter. Char.-The most common colour is a bright olive green, sometimes of an apple green, pistachio, or mountain green; a wine, honey, or orange yellow, and sometimes also a reddish brown, and browuish black; but these latter varieties are rare. It is found in rounded pieces, from the size of the head to that of a grain of millet, most commonly included, and disseminated in basalt. It has been found crystal

lized.

Internally,

Localities, &c.-Olivine is found in different countries, as in Bohemia and Saxony, and in Vivarais in France, and most commonly in rounded pieces in the cavities of basalt. Brochant says that it has not been discovered in the basalts of Ireland, England, Sweden, Norway, and Italy. We have, however, collected specimens of olivine among the basaltic rocks of the Giant's Causeway in Ireland.

Olivine and chrysolite are considered by Hauy as one species, and described under the name peridot. 4. Species. CocCOLITE.

Coccolithe, Brochant, ii. 504. Haüy, iv. 355. D'Andrada. Nich.. 4to. Jour. v. 495.

Exter. Char.-Colour, meadow green, olive, or blackish It is found in masses which are comgreen. posed of separate pieces, granular, in small grains, which may be easily separated; these grains are anguJar, and discover some appearance of tendency to crystallization.

Lustre, resplendent, vitreous; fracture foliated; cleavage double, as examined by Haüy, but single according to D'Andrada: it is hard, scratches glass; the grains are often translucent. Spec. grav. 3.316-to 3.373.

Chem Char-Coccolite is infusible without addition before the blow-pipe. With borax it melts into a pale yellow transparent glass, and with carbonate of potash Ento an olive green vesicular glass.

4

Localities. It is found in the iron mines of Hel- Siliceous lesta and Assebo in Sudermania, at Nerica in Sweden, and near Arendal in Norway.

5. Species. AUGITE..

Octahedral Basaltine, Kirw. i. 219. L'Augite, Brochant, i. 179. Pyroxene, Haüy, iii. 80.

Essen. Char-Divisible, parallel to the sides of an oblique rhomboidal prism, of about 92° and 88°, which is subdivided in the direction of the great diagonals of the bases.

gray.

Exter. Char.-Colour, olive green, black, white, and It is found sometimes in rounded pieces, and in grains, but most frequently crystallized. The primitive form is an oblique-angled prism, the bases of which are rhombs: the integrant molecule is an oblique triangular prism. The form of the crystals is generally a six and eight-sided prism, which is terminated by a two-sided summit. The crystals are commonly small, smooth, and brilliant, sometimes a little shining. Internal lustre shining, and almost resplendent, resinous. Fracture perfectly foliated; cleavage double; translucent at the edges; harder than olivine; gives lively sparks with steel, and scratches glass; rather brittle; spec. grav. 3.226 to 3.777.

Chem. Char.-Fusible before the blow-pipe with difficulty, and only in small fragments, which melt into a black enamel.

La Vesuvienne, Brochant, i. 184. Idocrase. Haüy, ii. 574.

Essen. Char.-Divisible parallel to the faces and diagonals of a rectangular prism, with square bases; melts into a yellow glass.

Exter. Char.-Colour brown, orange, dark green, and yellowish green.

This mineral is found massive, disseminated, or cry.stallized. Primitive form, a rectangular prism, little different from a cube; integrant molecule a triangular prism. The forms of its crystals are, a rectangular prism, with four sides, truncated on all its edges, or truncated on its lateral edges; or a six-sided prism truncated on all its edges. The crystals are usually small, single sometimes, and sometimes in groups. Lateral planes longitudinally streaked. U

か

Some are smooth;

genus.