572 Reports and Proceedings — Geological Society of London. 



The Author next treats of the chemical deposits of the Azoic 

 system, gives a provisional scheme of classification of ores, and 

 discusses the origin of ore deposits. 



The rocks of the Palaeozoic system are next described, and it is 

 maintained that the eastern sandstone of Lower Silurian age 

 underlies the copper-bearing or Keweenawan rocks. The veins and 

 copper deposits are described in detail, and the paper concludes 

 with some miscellaneous analyses and descriptions, as well as a list 

 of minerals found in Michigan. 



2. "The Gold-quartz Deposits of Pahang (Malay Peninsula)." 

 By H. M. Becher, Esq., F.G.S. 



The gold-quartz deposits of Pahang which traverse an extensive 

 series of slates, sandstones, and dark-coloured limestones, sometimes 

 more or less metamorphosed, and probably of Palceozoic age, occupy 

 the low-lying hill-country on the eastern side of the central granitic 

 mountain-range. The prevailing dip of the strata is eastward. 



In some places the auriferous rock penetrates adjacent intrusive 

 syenites, but has not been traced in connexion with the main granitic 

 'massif which is generally considered to be the matrix of the cas- 

 siterite found in the ' Straits' alluvial Tin-fields. 



The gold occurs in lodes and irregular formations, which, however, 

 are not distinguished from one another by any hard-and-fast line ; 

 the diiference depends on the size, shape, and continuity of the 

 quartz veins, though even the lodes seldom maintain their regularity 

 for more than a few score feet. The quartz often occurs in very 

 narrow veins intersecting one another to form what may be called 

 * stockworks.' It is probably from these minute veins that the 

 alluvial gold is derived. In the Raub mine numerous rich veinlets 

 occur in a certain zone where the whole slate-rock is charged with 

 iron pyrites, probably auriferous. Many ' stockworks ' are intimately 

 associated with dykes or intrusions of a rock which may be called 

 trachyte-porphyry, and these igneous rocks are decomposed where 

 prominently associated with auriferous quartz. 



3. "The Pambula Gold-deposits." By F. D. Power, Esq., F.G.S. 

 The Pambula Gold-field is situated in the parish of Yowaka, 



County of Auckland, in the South-eastern corner of New South 

 Wales. 



The lodes are different from ordinary auriferous deposits, inasmuch 

 as the material filling the ore-channels does not differ greatly in 

 appearance from the ' counti-y ' rock, and is but slightly mineralized. 

 The ' country ' rock is • pyrophyllite schist,' associated with ' felspar- 

 porphyry,' sometimes turning into ' quartz-porphyry,' the whole 

 being tilted at a high angle. The bedding and cleavage-planes 

 appear to be coincident. The rock forms lenticles both microscopic 

 and macroscopic. Some of the lodes are accompanied by a quartz 

 ' indicator ' which contains little or no gold in itself, the precious 

 metal being found in the shattered ' comitry ' rock of its foot-wall. 

 On the foot-wall side this shattered zone gradually merges into the 

 ordinary ' country ' rock. The cause of the parallelism of the 

 auriferous lodes, the mountain-ranges, and the seacoast is discussed, 

 and it is pointed out that the gold does not occur in large grains. 



