THE DIAMOND. 



The Diamond is generally conceded to 

 be the most beautiful as it is the most im- 

 portant of precious stones. While other 

 stones at times exceed it in value, weight 

 for weight, in total importance as an ar- 

 ticle of commerce other gems are hardly 

 to be compared with it. Out of thir- 

 teen and one-half millions of dollars' 

 worth of precious stones imported into 

 the United States in 1900, twelve million 

 dollars' worth were Diamonds. Not all 

 this amount was employed for jewelry, 

 since there is a large utilization of the 

 stone for industrial purposes, but even 

 for jewelry the Diamond has a largely 

 preponderating use. Its points of supe- 

 riority are its hardness, high refractive 

 powers and hence play of colors, its trans- 

 parency and its luster. In all these qual- 

 ities it excels any other known mineral. 

 Hence when in addition to these it ex- 

 hibits different body colors, as is some- 

 times the case, no other gem can equal 

 it in value. 



Usually the Diamond is colorless or 

 white, although shades of yellow are also 

 common. It is also known in shades of 

 red, green and blue and in brown and 

 black. The two latter are rarely trans- 

 parent and grade into the varieties known 

 as bort and carbonado, which have no 

 value as gems but are highly important 

 for industrial purposes. 



In composition the Diamond is pure 

 carbon, thus not differing chemically 

 from graphite or such forms of carbon 

 as lamp-black, bone-black, etc. It is 

 crystallized, but this can be said of 

 graphite as well. Why carbon should 

 assume the form of Diamond in one case 

 and graphite in another, as well as being 

 amorphous in other occurrences, is not 

 known. Such behavior of a substance is 

 known as dimorphism, and numerous 

 illustrations of it are to be found in Na- 

 ture. 



Being pure carl>on. Diamond can be 

 liurncd in the air. The finely divided 



dust can be burned in the ordinary blow- 

 pipe flame, and for stones of ordinary 

 size a temperature of about 900° C is 

 sufficient. The possibility of consuming 

 the Diamond by heat is said first tO' have 

 been suggested by Sir Isaac Newton, who 

 reasoned from the high refractive index 

 of the stone that it was ''an unctuous sub- 

 stance coagulated," and hence probably 

 combustible. Following. this suggestion 

 two Italians, Averani and Targioni, suc- 

 ceeded in 1695 in burning some Dia- 

 monds in a furnace, and since then the 

 experiment has been repeated many 

 times. The Diamond does not fuse in 

 burning, but after becoming heated to 

 redness gradually grows smaller, emit- 

 ting sparks, till it entirely disappears. It 

 leaves no ash except in the case of the 

 impure form known as carbonado. The 

 gas given off has been collected and an- 

 alyzed and found to be carbon dioxide 

 just as would result from the combustion 

 of other forms of carbon. If protected 

 from the air or free oxygen, the Dia- 

 mond can be exposed to high heat with- 

 out change. 



Being a crystallized substance and ex- 

 cessively hard the Diamond is usually 

 found in the form of more or less per- 

 fect crystals. These have forms such as 

 the cube, octahedron, etc., which belong 

 to the isometric system, and it is in this 

 system that the Diamond crystallizes. The 

 crystals do not possess, however, the 

 highest isometric symmetrv, but belong 

 to the class designated by Groth as hex- 

 akistetrahedral, being tetrahedral with 

 inclined face hemihedrism. It is very 

 common for the faces to be curved in- 

 stead of flat and to show etching figures 

 of various kinds. The crystals are often 

 considerably distorted so as to produce 

 pointed and rounded forms, and twin 

 crystals are common. Although so ex- 

 cessively hard the edges of the crystals 

 as found in the beds of streams are often 

 rounded from the wear of the other peb- 



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