696 GOLD 



quantity of lode-stuff reduced was 3,500 tons, and the gold produced 1,606 ounces 

 (Dec. 1866). 



A brief reference to the various modes of gold-extraction used in Merionethshire 

 will bo interesting. 



In the earlier stages of gold-mining (1843) at Cwmheisian, the ore was finely 

 stamped and concentrated by washing apparatus, and afterwards amalgamated by 

 arrastras, or smelted. After this the gold-mines lay dormant until the Californian 

 discoveries in 1853, when rich gold-quartz was at the same time found at Clogau. 

 The amalgamating machines of Britten and Berdan were then introduced ; but it 

 was soon found impossible to work auriferous sulphides indiscriminately by tri- 

 turation in quicksilver. A good deal, however, of the rich ore at Clogau was treated 

 in this way with very profitable results ; but in some cases rich ore yielded only a 

 small portion of its contained gold, and generally much gold was found in the, 

 'tailings.' Washing apparatus was erected at the Cambrian mine, on the Marietta 

 plan, but with no satisfactory results. This method was improved by Mr. Bolt 

 at the Prince of Wales mine by the addition of shaking tables, and troughs of 

 quicksilver ; but the process only partly succeeded, there being very little gold in 

 the stuff, and that little associated constantly with heavy sulphides. Barrel amal- 

 gamation had been previously tried here, at a great cost, but failed for the same 

 reason. 



A mode of triturating the ores in quicksilver, having all the vices of Berdan, and 

 none of its virtues, was introduced at the old Dolfrwynog mine, together with an old 

 plan of forcing the ground ore through a body of quicksilver. It is not publicly known 

 whether this proceeding was a total failure or not. No gold appears to have been 

 accounted for, although some of the richest ore in Wales was found at this mine at the 

 time. The sluice-box principle was adopted at North Dolfrwynog on the alluvium, 

 with the object referred to ; but it was discovered that miich more gold was lost than 

 gained by the pursuit, and it was discontinued. 



Mitchell's amalgamators were next introduced at Cwmheisian, which were vessels 

 of quicksilver, through which the ground mineral was intended to be forced by 

 means of a succession of screws, in order that the particles of gold might bo 

 presented to the greatest possible surface of quicksilver, and for a long period 

 of time. This plan was found utterly useless with minerals containing sulphides in 

 excess. 



Sloper's plan of separating the metals by specific gravity was also tried on the 

 alluvium by the patentee, at North Dolfrwynog, and failed. 



In 1862, Mr. Mosheimer introduced his machinery at Grarthgell, Clogau, Cwm- 

 heisian, and Castell Cam Dochan. After stamping the minerals in the usual way, 

 Mr. Mosheimer at that time proposed to grind them in his horizontal pans with 

 heated quicksilver, adding chemicals, occasionally, for the purpose of liberating 

 the gold from the sulphides. At Cwmheisian this plan was useless because of 

 the sulphides. The quicksilver constantly became 'sick,' dragged in strings after 

 the mullers, and lost apparently all its natural affinity for gold. Only a very small 

 portion of the contained gold was extracted, and the rest left in the tailings. 



At Clogau and Castell Carn Dochan, however, the results wore very different. 

 The quartz-lodes at these mines are comparatively free from sulphides, there is a littlo 

 bismuth sulphide found at Clogau, and a littlo iron sulphide at Castell Cam Dochan 

 but at both mines, without heating the quicksilver, or introducing chemicals, the gold 

 was practically all extracted ; from the richer minerals by Britten's and from the bulk 

 by Mosheimer's machines. 



In 1866 the gold reduction works at Castell Cam Dochan were the most complete. 

 There, the ore-stuff as it comes from the mine was taken direct to the stamps, 

 reduced very fine, the metalliferous particles concentrated on blankets, the blanket 

 sand further concentrated, and then amalgamated in the ' Mosheimers ' and 'Brittens ; ' 

 all the waste water, &c. passed into shaking boxes containing quicksilver, and thenco 

 through a series of Hungarian pans, such as are used at Schemnitz. The gold hero 

 being all free, scarcely a trace of gold was ever found in the tailings. The same plan, 

 with some modifications, was successfully used at Clogau. 



A long experience has now elicited that sulphides of lead, arsenic, antimony, zinc, 

 bismuth. &c. will frequently so envelope small particles of gold with a film or tarnish, 

 that quicksilver cannot touch it. The trituration of such sulphides in quicksilver 

 generally destroys its fluidity and amalgamating power, or reduces it to minute glol ailrs. 

 which, owing to the tarnish they also have by some means acquired, refuse to re-unit'-, 

 and are consequently washed away with the tailings. Hence a great loss of l*oth 

 quicksilver and gold, because generally these minute globules, so washed away, are 

 really gold-amalgam. Again, the quicksilver of commerce is very seldom in a fit Mato 

 for complete amalgamation, even of free gold, and it is well known also that tho 



