BY G. THUREAU, F.G.S, 3 



it possible then, I may ask, that these almost non-auriferous 

 iron bi-sulphides produced on their supposed (inert) decom 

 position that peculiar purple mineral, assaying, as reported, 

 •considerably above 170ozs. of gold per ton ? Again, those so 

 very solid pyrites contain no barytes, which latter minerals I 

 first discovered as the necessary adjunct to the gold. " Ex 

 nihil aut nihilo fit." 



It may also be fairly questioned how it is that these veins 

 or beds of pyrites, so dense in character, must have un 

 doubtedly withstood atmospheric influences for immeasurable 

 periods, on decomposition (?) filled, with new substances 

 resulting from that process, over 50 feet in width by over a 

 mile and a half in length, and to unknown depth of an open 

 fissure with a "solution" only. Such a fissure or chasm 

 would have collapsed at the sides long before the decomposition 

 process had even been initiated, as the adjacent and super- 

 incumbent rocks could not have withstood the lateral and 

 vertical pressure their own great gravity would produce, had 

 not the walls of that fissure been kept apart by some heavy 

 filling material of a homogenous kind, exerting in itself a 

 sufiiciently powerful resistance to the overhanging walls of 

 this fissure. 



Supposing, however, decomposition was the cause and effect 

 of this rich aggregation of minerals and metals, or, in the 

 authors own words : " That it (the Iron Blow) is the result of 

 oxidation of pyrites similar to that now so largely associated 

 with it ; the hydrated oxide first formed, being subsequently 

 metamorphosed sufficiently to get rid of its combined vajjour 

 and produce the slight change in the form of disseminated 

 'particles of harytes, as revealed by the microscope ; or, this 

 process may have occurred during the process of oxidation," 

 etc., etc. 



It will therefore be necessary to bear in mind that, as 

 proved from analysis, we have, firstly, a nearly non-auriferous 

 bi-sulphide of iron (pyrites) to deal with, containing no baryta 

 to speak of ; and secondly, that water is assumed to have 

 produced the rich pulverulent gold rock by means of the 

 decomposition of the former, and contemporaneously or subse- 

 quently by means of infiltration filled the fissure, and that 

 small (?) disseminated particles of baryta appeared either 

 before (whence ?) or during the process of oxidation. 



Now, it is a fact that baryta is the " matrix" of that purple 

 rock, exceeding " thirty (30%) per cent, of the whole of the 

 vein-matter, being disguised by coatings and linings" of 

 specular iron, and exhibiting gold in fine crystalline and 

 filagree forms ; that auriferous rock likewise exhibits a dis- 

 tinctly recognisable vesicular structure, the cells and cavities 

 being now, however, filled by means of similar rock of a 



