BY L. A. COTTON. 809 



It is to be expected, therefore, that the gravels and sands would 

 consist of simple products, and, with regard to the great bulk of 

 them, this is true. There are, however, to be found, intersecting 

 the granite, a great number of small reefs containing many 

 different minerals. It is from these reefs that the bulk of the 

 wash is made. The hard parts of the wash comprise quartz, 

 tourmaline, topaz, jasper, zircon, cassiterite, garnet, and diamond. 

 The soft parts are made up of kaolin, decomposed granite-pebbles, 

 and decomposed pebbles of basic igneous rock. 



In the main lead, the wash is fairly coarse, the average size of 

 the pebbles ranging from 1 to 8 cm. in diameter. Occasional 

 boulders are met with, from this size up to several feet in 

 diameter. 



A large percentage of the hard wash-pebbles are quartz, pro- 

 bably more than 90%; and these can have been derived only 

 from the reefs in the granite. Tourmaline-pebbles are next in 

 order of abundance. These are not of large size, being, as a rule, 

 rather less than 1 cm. in length. They are generally more bean- 

 shaped than the quartz-pebbles, this, no doubt, being due to their 

 formation from the "pencil-tourmaline" so common in the quartz- 

 reefs. The proportion of tourmaline to quartz-pebbles varies 

 greatly from place to place, but rarely exceeds 5 %. The topaz, 

 which occurs in the wash, has, no doubt, been derived from the 

 same source as the tourmaline, but the amount present is very 

 small, and is* only noticeable when concentration has been 

 effected. A similar statement also applies to the garnet found 

 in the leads. These gems are small, rarely exceeding 4 mm. in 

 diameter. It is this mineral more than any other which is con- 

 stant in its association with the diamond. Sapphire is only 

 occasionally met with in association with the Copeton diamonds, 

 and zircon is a rare associate, but special characteristics distin- 

 guish the wash from different parts of the lead. The thickness, 

 the degree of coarseness, and the relative amounts of the various 

 constituents, are all very variable quantities. At Soldier Hill, 

 a number of sharp, angular quartzes are present in the wash, so 

 that, doubtless, a reef is close to this deposit. Here, also, a 

 number of jasper-pebbles occur. These are grey stones, much 



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