212 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



in his mouth, or smear it with grease ; and when it must be sent on a journey it will often 

 be placed inside a potato, this being considered the safest method of packing such stones, 

 probably because they are thereby protected from contact with other diamonds or hard 

 objects, the slightest scratch being sufficient to bring about the bursting of the stone. The 

 singular behaviour of these stones is due to the existence of intense internal strains in their 

 substance ; the same phenomenon being also the cause, as we have seen, of the strong 

 anomalous double refraction possessed by some diamonds. 



The collective characters of the stones found in each mine and in each part of a mine 

 are distinctive, but single stones of evei-y quality occur in all mines. Thus, though it 

 may be impossible to state the particular mine in which a single stone was found, yet 

 an experienced Kimberley diamond merchant would have no difficulty in naming the 

 mine, or portion of a mine, from which a parcel of stones had come, provided that the 

 parcel formed a fair sample of the yield of that particular deposit. 



The stones found in the rich Kimberley mine are usually poor in quality; and 

 broken fragments, the latter invariably uncoloured but containing many black enclosures, are 

 present in great abundance. A large percentage of the material yielded by this mine, 

 especially from the north side, is unsuitable for cutting and only applicable as bort, 90 per 

 cent, of South African bort being furnished by this mine. Broken fragments are confined 

 to a certain extent to the middle and south side of the deposit ; while the north-east 

 corner and the west side of the mine have yielded brown octahedra and " smoky stones " 

 in great abundance ; yellow diamonds, so numerous everywhere else, are here almost 

 wholly absent. The stones found in the east and south-east portions of the deposit 

 closely resemble those from Du Toifs Pan mine. 



From the De Beer's mine are obtained crystals of every kind and colour, the surface 

 of which is almost invariably finely granular, glimmering, and somewhat greasy, surface 

 characters which are met with in crystals from no other deposit. Bort is rare, but broken 

 fragments containing black specks are abundant. Large yellow rhombic dodecahedra are 

 very frequent, the De Beer's stones being, on the whole, remarkable for their large size, 

 while stones from the Kimberley mine are conspicuous for their whiteness. 



The diamonds found in the Du Toit's Pan mine are usually well crystallised and of 

 considerable size, yellow octahedra being often specially large. Bort, very small stones and 

 " smoky stones," are practically absent, and crystals disfigured by black specks are seldom 

 met with. The colour of stones from this mine is often rather dark, but the proportion of 

 Cape white and yellow stones found is greater than elsewhere in this region. On the whole, 

 the diamonds yielded by this mine are more beautiful than those of any other deposit in 

 the neighbourhood of Kimberley. 



The Bultfontein mine yields principally small white octahedra, much modified on 

 their edges and usually full of faults and spots. Large stones, broken fragments, bort, and 

 deeply coloured stones are here practically absent. 



The average value of stones from the different mines of course varies in correspondence 

 with the variations in quality we have just been noticing. In the first column of the 

 following table, compiled from the estimates given by Moulle, will be found the. average price 

 per carat of rough stones from the different mines during the period between September 1, 

 1882, and the end of March 1884. The corresponding prices for 1887, given in the 

 second column, are somewhat lower, but the proportion existing between them is about the 

 same and has indeed remained practically unaltered up to the present day. 



