Page:The American Cyclopædia (1879) Volume VI.djvu/84

 76 DIAMOND of a Greek merchant, who received for it from the empress $450,000, an annuity of $20,000, and :i title of nobility. The- Austrian diamond is of a beautiful lemon color, and cut in rose; !,f ia i:;:i c.-.rats. Its value is less than M IK- t'ut t<>r its color and the form in which it i> cut, ranking as worth $500,000 in- (X The most valuable diamond f.iunil in 'the I'nited States was picked up by a workman at Manchester, on the banks of the James river, opposite Richmond, in 1856. The locality i- in the tertiary formation, and the diamond originally belonged, no doubt, to the gold region up the river. It is of curvilinear octahedral form, specific gravity 3'503, and weighs 23-7 carats. It is lightly chatoyant, and would probably cut white ; but an original flaw was increased by the rough treatment it 1 from those into whose hands it fell, so that its value was greatly deteriorated. The process of collecting diamonds is similar to that of collecting gold in the alluvial deposits. The coarse gravel and rolled pebbles derived from the primary and metamorphic rocks form the lowest stratum among the sands and clays of the alluvium. This stratum, resting upon the surface of the rock, is the repository alike of gold and of diamonds. It is laid bare in the beds of the streams, when these cease to flow in the dry season, or are drawn off by sluices made for the purpose. From these beds, as well as from excavations in the bottom, the gravelly conglomerate or cascalho is removed, to l.e washed when convenient. This in Bra- zil is usually in the rainy season, and the work is done in a long shed, through which a stream of water is conveyed, and admitted into boxes in which the ccucalho is washed. A negro works at each box, and inspectors are placed ti watch the work, and to prevent the laborers from secreting the diamonds. It is the custom to liberate the negro who finds a diamond weighing 17$ carats. Dr. Beke, in a paper read at a meeting of the British association, relates that a slave in Brazil seeking for dia- monds in the bed of a river broke with his iron l.ar through a crust of silicious materials, ce- mented together by oxide of iron, in which he discovercil a bed of diamonds, which were afterward sold for $1,500,000. This immense quantity, being carried to England, so over- stocked the market that few of the English houses were able to stand up against it. Be- Mdrs their use as ornaments, diamonds are ap- plied to -eeral practical purposes. An impure diamond, but very hard, and colored black, known under the name of bort, is used for nniiiii;r the bit-* of the diamond drill (see 1 i- al-i crushed to fine powder in mortar, and n-.-d for routing the metal- lic di-ks employed by lapidaries for producing flat surfaces on pn-cions -tones of great hard- ness. ^ The tine splinters are made into drills, tor piercing small holes through rubies and other hard t,, n .-<. The property possessed by the diamond ,,f cutting glass is due not merely to its extreme hardness, but to the peculiarity of its crystallization in rounded faces and curvi- linear edges. The natural crystal only is suit- able for this purpose. The diamond exhibiting the physical properties of matter in their high- est state of perfection, and proving after all to be of the simplest chemical composition, it has been a matter of no little scientific interest to study the peculiarities of its construction, and to determine if possible the secret processes by which nature has elaborated the most perfect gem from so homely a substance as charcoal. Its high value has stimulated these researches, in the hope of individual profit by its artificial production. 'But though more complicated forms of matter have been successfully repro- duced, carbon has not yet been made to attain the simple perfection of the diamond, unless it be in crystals invisible to the naked eye ; nor have we yet learned from what department of nature's works the material has been taken, that has been so beautifully perfected. The vegetable kingdom may have furnished it, after itself receiving it from the atmosphere, or it may have been unlocked from those reposi- tories of carbon shut up from remote geological periods in the carbonic acid of the calcareous rocks, or from such collections of fossilized plants as are now seen in various stages of change to mineral substance. But if the direct object of these researches has not been attain- ed, the forces which have acted upon it to give to it some of its peculiarities have been par- tially determined, as also a previous condition in which it must have existed. Sir David Brewster, from the exhibition of polarized light around the minute and irregular cavities in diamonds, has concluded that the substance has once been in a soft state, and compressed in these parts by the expansive action of a gas or fluid contained in the cavities ; and as vari- ous circumstances indicate that this softness was not the effect of either solvents or heat, he is of opinion that, like amber, the diamond is a vegetable substance, slowly consolidated into a crystalline form. The nearest approach to its reproduction has been in the experiments of M. Despretz. By long continued voltaic action, carbon free from every trace of mineral substance, prepared from crystallized sugar candy, was made to deposit microscopic crys- tals in black octahedrons, in colorless trans- lucent plates, the whole of which had the hardness of the powder of the diamond, and which disappeared in combustion without leaving any perceptible residue. Being, how- ever, only in powder, it was impossible to iso- late and weigh these crystals, or to determine their index of refraction and angles of polari- zation. It is said that a similar result has been obtained by decomposing a mixture of chloride of carbon and alcohol by galvanic currents continued for six months. The principal Eng- lish works on the subject are D. Jeffrey's "Treatise on Diamonds and Pearls" (8vo, London, 1750); J. Mawe's "Treatise on Dia-