352 PRINCIPLES OF CHEMISTRY 



'of rare occurrence in nature, and is found in the alluvial deposits of 

 the diamond mines of Brazil, India, South Africa, &c. It has also been 

 found in meteorites. lf)bi8 It crystallises in octahedra, dodecahedra, 

 cubes, and other forms of the regular system. 16 The efforts which have 

 been made to produce diamonds artificially, although they have not been 

 fruitless, have not as yet led to the production of large-sized crystals, 

 because those means by which crystals are generally formed are in- 

 applicable to carbon. Indeed, carbon in all its forms being insoluble 

 and infusible does not pass into a liquid condition by means of which 

 crystallisation could take place. Diamonds have several times been 

 successfully produced in the shape of minute crystals having the 

 appearance of a black powder, but when viewed under the microscope 

 appearing transparent, and possessing that hardness which is the 

 peculiar characteristic of the diamond. This diamond powder is de- 

 posited on the negative electrode, when a weak galvanic current is 

 passed through liquid chloride of carbon. 16bis 



Moissan (Paris, 1893) produced diamonds artificially by means of 

 the high temperature attained in the electrical furnace 17 by dissolving 



is bt. Diamonds are found in a particular dense rock, known by the name of 

 itacolumnite, and are dug out of the dSbria produced by the destruction of the 

 itacolurnnite by water. When the debris is washed the diamonds remain behind ; they 

 are principally found in Brazil, in the provinces of Rio and Bahia, and at the Cape of 

 Good Hops. The dtbris gives the black or amorphous diamond, carbonado, and the 

 ordinary colourless or yellow translucent diamond. As the diamond possesses a. very 

 marked cleavage, the first operation consists in splitting it, and then roughly and finely 

 polishing it with diamond powder. It is very remarkable that Professors P. A. Latchiuoff 

 >and Erofeeff found (1887) diamond powder in a meteoric stone which fell in the Govern- 

 ment of Penza, in the district of Krasnoslobodsk, near the settlement of Novo Urei 

 (Sept. 10, 1886). Up to that time charcoal and graphite (a special variety, cliftonite) had 

 been found in meteorites and the diamond only conjectured to occur therein. The Novo 

 Urei meteorite was composed of siliceous matter and metallic iron (with nickel) like 

 many other meteorites. 



1(5 Diamonds are sometimes found in the shape of small balls, and in that case it is 

 impossible to cut them because directly the surface is ground or broken they fall into 

 minute pieces. Sometimes minute diamond crystals form a dense mass like sugar, and 

 this is generally reduced to diamond powder and used for grinding. Some known 

 varieties of the diamond are almost opaque and of a black colour. Such diamonds are 

 as hard as the ordinary ones, and are used for polishing diamonds and other precious 

 stones, and also for rock boring and tunnelling. 



16 bi Hannay, in 1880, obtained diamonds by heating a mixture of heavy liquid 

 hydrocarbons (paraffin oils) with magnesium in a thick iron tube. This investigation, 

 however, was not repeated. 



17 The electrical furnace is an invention of recent times, and gives the possibility of 

 obtaining a temperature of 8,500, which is not only not obtainable in ordinary f tfrnaees, 

 but even in the oxyhydrogen flame, whose temperature does not exceed 2,000. The elec- 

 trical furnace consists of two pieces of lime, laid one on the other. A cavity is made in 

 the lower piece for the reception of the substance to be melted between two thick 

 electrodes of dense carbon. On passing a current of 70 volts and. 450 amperes a tem- 

 perature of 3,000 is easily obtained. At a temperature of 2,50d (100 amperes and 40 



