which so often injure the value of a 

 Diamond and prevent it from being of 

 the "first water." These inclusions miay 

 be simply small cavities, sometimes so 

 numerous as to make the stone nearly 

 black, or they may be particles of other 

 minerals, such as chlorite, hematite or 

 carbonaceous matter. If the latter, the 

 flaws can sometimes be burned out by 

 careful heating. 



As already remarked, the refractive 

 power of the Diamond is very high. The 

 rays of light entering it are bent at a high 

 angle, causing a large degree of what, is 

 called total reflection within the stone. 

 The effect of this is to hght the stone's 

 interior. Moreover, the rays of light are 

 concentrated on a smaller part of the 

 surface than is the case with less highly 

 refracting minerals and thus also internal 

 illumination is produced. The most im- 

 portant result of the high refractive 

 power of the Diamond is the wide dis- 

 persion of the spectrum, causing the red 

 rays to be widely separated from the blue 

 rays and strong lights of one color to be 

 transmitted to the eye as could not be the 

 case were the different rays less widely 

 separated. It is this power of flashing 

 different colored lights which gives the 

 Diamond one of its chief charms. The 

 index of refraction ranges from 2.40 for 

 the red rays to 2.46 for the violet rays. 

 Ordinary glass has an index of refraction 

 for the red rays of onlv 1.52 and for the 

 violet 1.54, making the spectrum only 

 about half as long as that produced by 

 the Diamond. 



Another pleasing property of the Dia- 

 mond is the fact that it is usually more 

 brilliant by artificial light than by natural, 

 although some individual stones have a 

 reverse behavior. 



Diamond is much the hardest sub- 

 stance known in Nature, and as the prov- 

 erb says only the Diamond is able to ''cut 

 Diamond." It is ranked 10 in the scale 

 of hardness on which minerals are classi- 

 fied, corundum being the next below it. 

 It is really separated by a wide gap from 

 the latter mineral, however, and its hard- 

 ness is as much greater than that of 

 corundum as that of corundum is greater 

 than that of the first mineral in the scale. 

 This hardness of Diamond affords a 

 ready means of identifying it, as it will 

 scratch all other substances. It is popu- 



larly supposed that Diamond is the only 

 mineral which will scratch glass to any 

 extent, and a stone found, is often re- 

 ported to be Diamond because it will do 

 this. As a matter of fact, however, all 

 quartz will scratch glass and the harder 

 minerals, garnet, topaz, beryl and others 

 will do so easily. Minerals which will 

 scratch glass are therefore common. The 

 Diamond cuts glass instead of scratching 

 it, and is the only mineral that will do 

 this. Although the Diamond is so hard, 

 it is not tough, and can be easily broken 

 with the blow of a hammer. It was a tra- 

 dition of the ancients that if a Diamond 

 were put upon an anvil and struck with a 

 hammer, both hammer and anvil would 

 be shattered without injuring the Dia- 

 mond in the least. One occasionally 

 hears this statement made even at the 

 present day. It is entirely untrue, how- 

 ever, the Diamond being as brittle as at 

 least the average of crystallized minerals. 

 The specific gravity of the Diamond is 

 about three and one-half times that of 

 water, determinations showing variations 

 between 3.49 and 3.53. Carbonado is 

 lower, ranging between 3.14 and 3.41. 

 Diamjond is thus a comparatively heavy 

 mineral, the only ones among the gems 

 which much exceed it in specific weight 

 being hyacinth, garnet, ruby, sapphire 

 and chrysoberyl. 



Diamond becomes strongly electric on 

 friction so that it will pick up pieces of 

 paper and other light substances. It does 

 not retain its electricity long, however, 

 usually not over half an hour. It is not 

 a conductor of electricity, differing in 

 this respect from graphite, which is a good 

 conductor. Diamond becomes phosphor- 

 escent on rubbing with a cloth, giving 

 out a hght which is visible in the dark. 

 Some stones emit such a light after being 

 exposed to the sun's rays for a time, as if 

 they took it up from the sun and gave it 

 out again. This has often been stated 

 . to be a property of all Diamond, but this 

 is not true, only certain stones exhibiting 

 it. As first suggested by Mr. Geo. F. 

 Kunz, it is probable that this phosphor- 

 escence is due to minute quantities of hy- 

 drocarbons which emit light on being 

 lieated by the friction given the stone. 

 It is curious to note that the light is in 

 some cases given out only from certain 

 crvstal faces" of the stone. Thus Dia- 



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