219 



approximate only, and of course refer only to the very small 

 specimens received) and from the description of occurrence 

 in report by Inspector of Mines, and there seems little 

 room for doubt that the ' Iron Blow ' is the result of oxi- 

 dations of Pyrites similar to that now associated so largely 

 with it ; the hydrated Oxide first formed being subse- 

 quently metamorphosed sufficiently to get rid of its com- 

 bined water, and produce the slight change in the form of 

 the small disseminated particles of barytes, as revealed by 

 the microscope ; or this change may have occurred during 

 the process of oxidation. By oxidation three parts by 

 weight of Iron Pyrites would yield two parts of Iron 

 Peroxide." 



From these analyses it would seeni that the presence of 

 barytes with iron and sulphur in the monster " Iron Blow" 

 does not present any greater difficulty as regards mode of 

 origin than is to be found in determining the mode of origin 

 of the ordinary auriferous quartz or other metalliferous 

 veins. I quite agree with Mr. Thureau in regarding 

 the deposit as a most extraordinary one so far as 

 auriferous workings are concerned, although the association 

 of barytes in a small crystalline form with gold is known to 

 occur in one or two gold mines in New South Wales, notably 

 at the Canobolas and Winterton mine, Mitchell's Creek, near 

 Bathurst. 



Barytes is also often present in veins of lead, silver, and 

 other minerals as the gangue of the ore, and as at the Linda 

 it often occurs as an accessory, in a lamellated form, notably 

 in the clay strata of Monte Perno, near Bologna. 



Whether we suppose that the " Iron Blow " is due to hy- 

 drothermal agency or not, there is nothing in the composi- 

 tion of the pyrites or dark purplish rock which necessitates 

 their having been formed originally in the way of " volcanic 

 mud." It is more probable that the four principal elements, 

 iron, barytes, sulphur, and gold, were originally precipitated 

 together from solution. There is not the slightest corres- 

 pondence between the Mount Morgan and Mount Lyell auri- 

 ferous deposits. 



Mr. Jack considers the aiiriferous formation at Mount 

 Morgan to be derived from a thermal spring or geyser during 

 the Tertiary age, and adds that " the frothy silicious sinter 

 agrees in every respect with the deposits of New Zealand and 

 Iceland geysers, and of the still more wonderful hot springs 

 of the Yellowstone National Park." There is little re- 

 semblance between the silicious sinter, without definite 

 bounds,of Mount Morgan, and the defined " fissure" at the 

 Linda with its auriferous peroxide of iron and barytes, and 

 I am inclined to the opinion that the formation at the latter 



