MINERALOGY, STS) 
substances whose crystals cannot all be referred to the same system; it is 
therefore dimorphous. The crystals of native sulphur are rhombic octahe- 
drons (pl. 33, figs. 4, 26, 27, 28, and 29), whose sharp solid angles are 
frequently truncated, as in fig. 27. Those crystals, however, which shoot 
out in melted sulphur when cooling, belong to the monoclinic system; they 
appear generally in the shape of long, thin, and brittle needle-shaped 
crystals, as shown in fig. 3. Sulphur has a resinous lustre, is sub-translu- 
cent, and gives out a peculiar odor when rubbed. It readily melts by the 
application of heat, and then takes fire when exposed to the air, burning 
with the production of sulphurous acid gas, and a suffocating odor. Native 
sulphur is of frequent occurrence in different formations, but rarely in large 
quantities. The finest crystals are found in the valleys of Noto and 
Mazzaro, in Sicily. It is found in very large quantities about recent or 
extinct volcanoes, as in the Solfataro near Naples. Sulphur often occurs in 
an impure earthy condition in large masses, and is deposited from sulphur 
springs. Most of the sulphur of commerce is obtained from Sicily, or else 
is derived from the sulphurets. In combination with metals it is universally 
distributed, and in large quantities, and is obtained in the reduction of the 
metal as a secondary product. Its applications are very numerous, espe- 
cially in the different forms of matches, gunpowder, &c. 
2. Carbon. 
Carbon occurs in a naturally pure and crystallized state, under forms 
belonging to two different systems, namely, as diamond and as graphite. It 
likewise occurs in an amorphous condition as stone coal, impure by being 
mixed with the other ingredients forming the carbonized plant. The purest 
form of carbon, the diamond, exhibits a crystallization belonging to the 
regular system. The most common forms of the diamond are the regular 
octahedron ( fig. 42), and the regular octahedron with the faces of the rhombic 
dodecahedron (fig. 43). It more rarely occurs in cubes, tetrahedrons 
( fig. 51), and trigonal-polyhedrons. 
The diamond was first found in the East Indies. The most important 
diamond mines at present, are, in India, between Golconda and Masulipatam, 
in Brazil, and in Borneo and Malacca. Here they occur in alluvial soils, 
lying loose in the sands of plains, and in the beds of rivers, or in the ferrugi- 
nous clay and recent conglomerate composed of quartz grains cemented by 
ferruginous sand. Nothing certain is known of the origin of the diamond. 
Of all gems this is the most esteemed, adding to its other properties that of 
being the hardest known. Its refractive power is extraordinary, and 
Newton, as early as 1675, concluded from this quality, peculiarly high in 
bodies containing carbon, that the diamond must be combustible. Its 
combustion was first effected by the Florentine Academy in 1694, and 
Lavoisier, by proving it to consist of pure carbon, first announced its true 
nature. It is a non-conductor of electricity, and has a specific gravity of 
3.5. It occurs quite colorless, or else grey. brown, black, yellow, green, and 
blue. It is used very advantageously as a means of cutting glass; but its 
chief application is as an ornamental gem, after being ground in certain 
regular shapes, whose end is the production of the peculiar and sparkling 
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