516 



THE GEOLOGIST. 



Lest there should be any misunderstanding as to the average yield of gold 

 in the Dolgellev district, he begged distinctly to state that the average yield 

 would not, in his opinion, exceed half an ounce to the ton of ore ; but there 

 were several extraordinary exceptions to the rule in some of the quartz-lodes 

 of the district. 



A gentleman asked what was the cost per ton of crushing the quartz ? 



Mr. Readwin said that as the machinery was worked by water-power, the 

 actual cost of crashing per ton would, probably, be less than half-a-crown. 



Professor Smith expressed his surprise, as the cost per ton in Australia was 

 calculated on an average at one pound per ton. He referred to the fact that 

 most of the firms there used the Cornish stampers for crushing the quartz, and 

 that it answered the purpose well. 



Mr. Readwin said that he also had witnessed the operation of gold extraction 

 by means of stamp heads, and it was found to fail, in consequence of the finely- 

 divided state in which the gold occurred ; so fine, indeed, that it floated away 

 on the surface of the water and was lost ; the heavier portions were, of course, 

 retained. 



Mr. Readwin exhibited some extraordinary specimens of Welsh gold, and 

 offered to explain to any person interested, a process by which minerals anta- 

 gonistic to the free amalgamation of mercury and gold, can be successfully 

 treated. 



List of the Gold Localities of the Dolgelly District. 



At Cwmheisian Uchaf, gold has been found in galena, mundic, copper-pyrites 9 



quartz, blende, schist, and arsenical iron-pyrites. 

 Cwmheisian Issa, in galena and blende. 

 Dol-y-frwynog, in galena, quartz, baryte, and mundic. 

 North Dol-y-frwynog, extracted from quartz, copper-pyrites, and gossan. 

 West Dol-y-frwynog, in quartz, schist, and baryte. 



Tyddyngwladis, in argentiferous galena, copper-pyrites, clay-slate, talcose-schist, 



gossan, and blende. 

 Caegwernog, in galena. 



Berthllwydd, in argentiferous galena and arsenical iron-pyrites. 

 Prince of Wales Mine, in blende, galena, quartz, and clay-slate ; but princi- 

 pally associated with blende. 

 West Prince of Wales, extracted from quartz. 



The Cambrian Mine, in blende, carbonate of lime, schist, quartz, clay-slate, 

 iron-pyrites ; but chiefly in blende and quartz. 



Victoria Mine, extracted from quartz and gossan. 



Lachfraith, extracted from quartz and iron-pyrites. 



Wellington Mine, in quartz and copper-pyrites. 



Caegwain, extracted from quartz and galena, 



Vigra, extracted from gossan, quartz, and copper-pyrites. 



Clogau (South Grant), extracted from gossan, blende, quartz, and copper- 

 pyrites. 



Clogau (Middle Grant), traces of gold in copper-pyrites. 



Clogau (North Grant), from " Saint David's Lode*" in quartz, copper-pyrites, 

 carbonate of lime, talcose-schist, galena, and associated with telluric- 

 bismuth. 



