DIAMOND: OCCURRENCE IN SOUTH AFRICA 207 



ranks next to that of the Kimberley mine in richness, although it was at first very poor, only 

 yielding J carat to the cubic metre of rock. The yield, however, increased rapidly as greater 

 depths were reached ; at a depth of 300 to 400 feet it had increased tenfold, so that 3 J carats 

 of stones were then obtained from a cubic metre of rock. From the year 1882 to 1884< the 

 yield obtained by some companies varied between 1'28 and 3'52 carats ; the mean yield for 

 the whole mine was estimated at 3'15 carats per cubic metre of rock, worth, at the higher 

 price commanded by stones from this mine, £S 9s. 



The richness of this mine varies not only with the depth, but also at different places on 

 the same level. The best part of the deposit is not surpassed in richness by any part of the 

 Kimberley mine, while other parts are so poor that they are not worked at all. The central 

 portion is very rich, and extensions of this stretch out especially towards the north and south, 

 forming a great contrast to the western third of the mine, which is extremely poor. A 

 beautiful yellow octahedron, weighing 302 carats, was found in the eastei'n side of the 

 deposit, on March 27, 1884. 



The increased richness of the lower lying parts of the deposit led to an attempt being 

 made, soon after the opening of the mine, to excavate the deeper portions by means of 

 underground workings, leaving the poorer portions standing a.bove. The attempt was very 

 successful as far as yield was concerned, but, owing to the imperfect methods adopted, was 

 attended by so many accidents that it had to be abandoned. Since 1885, however, when, as 

 we have already seen, the construction of underground workings began to be more skilfully 

 engineered, the excavation of the deeper lying material has been resumed. 



The Bultfontein mine is situated 4840 yards to the south-east of the Kimberley mine. 

 A cubic metre of the surface material yielded only a small fraction of a carat, but here also 

 a rapid and regular improvement in the deposit as lower depths were reached was manifested, 

 the yield at a depth of 200 feet having increased threefold. The increase in the richness of 

 the deposit took place in this mine with almost mathematical regularity, and was attended 

 both by an improvement in the quality of the stones, and by a diminution in the number of 

 fractured crystals. In 1887 a depth of 460 feet had been reached, a depth which has never 

 been exceeded in open workings. In the period 1881 to 1884 the yield varied between 0'56 

 and 1'27 carats per cubic metre of " blue ground," the mean yield being about 1"05 carats, 

 so that a cubic metre of rock contained diamonds to the value of about 23*. Underground 

 workings have not yet been established in this mine so that from it may be derived an idea 

 of the appearance presented by the other mines in earlier days. 



Du Toit's Pan mine is 1320 yards distant from Bultfontein mine, and 3542 from 

 De Beer's mine. In 1874 the mine was almost deserted, the yield being so small, and it has 

 only been systematically worked since 1880. Here again the surface rock was poor, and 

 yielded at the best of times only J carat per cubic metre of material ; here also the deposit 

 improved at greater depths, but not so rapidly as in the De Beer's mine. At a depth of 175 

 feet, at which the yield had doubled itself, a peculiarity not hitherto noticed in any other mine 

 was observed : the richness of the deposit was found to be absolutely identical at all points 

 on the same level, so that no variation in the yield was experienced. From this point down- 

 wards the yield rapidly increased, approaching that of the Kimberley and De Beer's mines. 

 From 1881 to 1885 the yield varied between 0"31 and 1*11 carats, the mean yield being 0'77 

 carat per cubic metre of " blue ground," having the average value of 22,?. In this mine, as 

 in the Bultfontein mine, the increase in richness of the deeper lying deposit was accompanied 

 by an improvement in the quality of the stones, and by a diminution in the number of 

 broken crystals. The open workings were here excavated to a depth of over 400 feet, and 

 underground workings have been scarcely as yet commenced. 



