﻿322 Mr. D. Forbes's Researches in 



It must be remembered, however, that gold in minute quan- 

 tity is undoubtedly contained in some of the English lead and 

 copper ores, especially when these ores are strongly argentiferous, 

 as will be hereafter noticed. Still the total amount of gold 

 present in such cases is so extremely insignificant as neither to 

 entitle them to the appellation of gold ores proper, nor even, in 

 most if not all cases, sensibly to augment the value of the ore 

 itself, since, as a rule, its value would scarcely be found to cover 

 the expense of its extraction or separation from the other metals 

 with which it is associated in the ore as it comes from the mine. 



In Devonshire the Poltimore mines at North Molton are tra- 

 ditionally reported to have been worked for gold by the Romans 

 during their occupation of Britain; and in 1853 the brown and 

 red u gossans" forming the substance of this lode at its surface- 

 outcrop or " backs/' as it is called by the miners, were treated 

 as gold ores, and stated to yield between one and two ounces of 

 fine gold per ton of " gossan." Still, although a not inconsider- 

 able amount of gold was extracted from them, the final result of 

 the adventure did not prove remunerative. The chemical exami- 

 nation of these " gossans," made by myself in 1854, indicated 

 that they were a product of the decomposition of slightly aurife- 

 rous metallic sulphides (principally iron), due to oxidation and 

 other atmospheric influences; and whilst it proved that these 

 gossans did contain a small amount of gold, it at the same time 

 showed that the actual amount present in them was much less, 

 and much more irregularly disseminated throughout the mass, 

 than had generally been reported. 



Native gold along with stream-tin ore (cassiterite) has also 

 been washed out of alluvial deposits at Shepstor in Dartmoor, 

 which have no doubt been formed from the debris arising from 

 the disintegration of the granitic rocks of that district. 



Native Gold from Cornwall. 



In this district the occurrence of gold in situ in its original 

 rock-matrix is extremely rare; but it is reported to have been 

 found in a cross course in Huel Sparnon, and the gossan of the 

 Nangiles mine is said to be auriferous. In the British Museum 

 a specimen of gold in quartz along with argillaceous or possibly 

 chloritic slate is exhibited ; but as no locality is given besides 

 Cornwall, I am uncertain as to whether it is to be regarded as 

 thoroughly authentic or not. 



In a recent visit to the north of Cornwall I found that the 

 argentiferous tetrahedrite (Freibergite), chalcopyrite, and galena 

 from a lode at Bound's Cliff near St. Teath, contained a minute 

 bui distinct amount of gold ; but I have as yet not been able to 

 determine its amount quantitatively. 



