ON THE KOCKS OF THE HAURAKI GOLD-FIELDS. 271 



separated from a quantity of rock free from all appearance of 

 quartz veins, and these, when separately assayed, gave no positive 

 indication of gold ; but some pyrites from the Long-drive Claim, 

 selected with the greatest care, so as to avoid anything like a 

 quartz vein, gave distinct traces of gold.* This is the only 

 analysis tliat I can lind which gave positive results, and it is of 

 great importance; but numerous assays of pyrites _ taken at 

 dili'erent distances from reefs are required before this point can be 

 considered as settled. 



A piece of carbonised wood, about an inch in diameter, highly 

 charged with pyrites, was found in the Maid of England Claim, 

 Waiotahi Creek ; the pyrites here being probably due to the 

 organic matter having reduced the iron sulphate which circulates 

 thi"ougli the rock. This pyrites was examined by Mr. W. Skey, 

 who reported that it contained no gold.f Sir James Hector, 

 however, says that " the specimen was not sufficiently large to 

 give a reliable indication of the presence or absence of gold,"| so 

 that the evidence is not conclusive ; but as far as it goes, it is 

 against the idea of iron sulphate containing gold in solution. I 

 am not aware of the iron sulphate, found in the old drives, having 

 been tested for gold. 



If it should turn out that pyrites in the country rock is an 

 indication of gold in the neighbouring veins, but that the pyrites 

 is not decomposed and is non-auriferous, then I would suggest 

 that, as part at least of the pyrites has been formed from 

 magnetite, the gold may have been originally in the magnetite 

 and have been released during the formation of the pyrites. I do 

 not think that this has been the case, but it is a point worthy of 

 investigation by the chemist. The pyrites is no doubt a secondary 

 mineral formed in the rock after consolidation, and if it should 

 turn out to be generally auriferous, we mvist suppose either that 

 the gold came from below with the sulphui', or that its source 

 is the titaniferous magnetite, which is one of the original con- 

 stituents of the rocks. 



But there are other secondary minerals constantly associated 

 with the gold veins, which must not be OA^erlooked. They are 

 chlorite and bastite. As chloritic-andesites, or propyl ites, are also 

 found in Nevada and in Hungary as well as at the Thames, and 

 as in all three places tliey contain gold and silver in remarkably 

 similar proportions, it would seem a priori that the chlorite might 

 be connected with the occurrence of the precious metals in veins. 

 Now Prof. F. Sandberger has proved that the mica of the gneiss 

 of the Black Forest contains small quantities of several metals 

 including silver, and other observers " have shown that a large 



* Reports Geological Explorations, 1870-1 pp. 84-5. 

 t Laboratory Reports No. 4, 186i), p. 17, No. 465. 

 X Reports Geological Explorations, 1868-69, p. 32. 



