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ridges and peaks, due partly to the unequal manner in which the different 

 kinds of rocks have resisted denudation, but we must also take into account 

 the effect of great dislocations which appear to have affected this district at a 

 late geological period, for we find at considerable altitudes masses of Tertiary 

 Limestone that are unknown at the same elevation in the eastern district. The 

 schist rocks in this western district are less uniformly foliated than we find 

 them in the east. They also afford a much greater variety of minei^als, and 

 even become truly crystalline, in son e instances, where dyke rocks intersect 

 them, so that the district may be compared to the north-west district of 

 Nelson. 



Several quartz reefs have been mined in this district, on the Shotover and 

 Arrow rivers, and much expensive machinery carried into very inaccessible 

 positions, but these adventures have not proved so successful as was anticipated. 

 However they were commenced at the time the great exodus of diggers took 

 placs to the western gold fields, which may account for the reefing capabilities 

 of the country not being better explored. Judging from its geological structure 

 the north-western district of Otago is the most likely part of the province 

 for the occurrence of mineral lodes. 



Before leaving the subject of our gold fields, the general mode of the 

 distribution of the alluvial deposits in New Zealand deserves a further descrip- 

 tion. This subject is important, as most of the mineral wealth, hitherto 

 obtained, has been from this class of deposits, which is generally associated 

 with iron-ore dust or sand, the black sand of the miners, so that these minerals 

 may be considered together. The source of these, like all other sands, is from 

 the disintegration of a parent rock, and together with the other elements of 

 the rock, they constitute what is known as "drift." Gold drift consists of sand 

 and gravel containing gold, and is formed by the action of running water in 

 streams, or water in motion, as along a sea or lake beach. The same action 

 causes the re-assortment of the materials, so that the heavier particles become 

 separated from the lighter, and it must be borne in mind that no other agent 

 than water in motion can exercise this sorting influence. It is therefore not 

 merely the existence of auriferous rocks at the surface in a district which 

 determines the extent and richness of the alluvial diggings, but we must also 

 take into account the amount of disintegration of these rocks, and also the 

 degree of concentration to which the detritus has been subjected. As might 

 be expected, alluvial gold is found to vary in composition according to the 

 nature of the rock which formed the original matrix • thus in Otago the gold 

 is pure or only alloyed with a little copper ; at Whakamarina, silver appears in 

 the proportion of 7 per cent., while on this side of the Strait it contains double 

 that proportion ; and in the north, at Auckland, though the alluvial gold does 

 not contain the same proportion of alloy, as that obtained from the reefs, 

 which is a circumstance that has been remarked on all gold fields, still it is 

 less pure, as a general rule, than the gold from the above-mentioned localities. 



In the South, the gold is associated on the other hand with platina, 

 zircons and garnets, and in the Nelson province with the rare mineral, Osmiri- 

 dium. In like manner the iron sand varies in composition. In the neigh- 

 bourhood of basaltic rocks, as at Dunedin, it contains 75 per cent, of titanite 

 of iron, which is a refractory compound of the oxides of titanium and iron, 

 while in some parts of the interior of Otago the sands consist either of 

 magnetite or lodestone, or of haematite, both of which are pui'e oxides of iron 

 and more valuable as ores. On the West Coast the sand has also the latter 

 character, and it is worthy of remark that, notwithstanding its proximity to 

 volcanic rocks. The well-known Taranaki iron sand, from its containing only 

 8 per cent, of titanic iron, apparently belongs to the sands derived from the 

 older rocks principally syenites and altered greenstone slates. 



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