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IMC Exploration (IMCP) – Modern Mining in the Vale of Avoca.
Excerpts from a brief history of metal mining in the Vale of Avoca, County Wicklow – by Alan Thomas and Peadar McArdle – Published by IMC Exploration (IMCP)
Modern Mining in the Vale of Avoca (1958-1982)
Mining in the Avoca Valley between 1958-1982 relied for the greater part on underground trackless mining – extracting large tonnages of lower grade ore in the West Avoca area at Ballygahan and Ballymurtagh
. Open pit mining was mostly from the east side of the river at Tigroney and Cronebane. From 1958-1962 St Patrick’s Copper Mines Ltd was responsible for the introduction of the relatively new trackless method of underground mining which enabled larger tonnages to be mined and consequently lower grades could be economically extracted. This entailed driving an inclined tunnel from surface down at a gradient of 1 in 8 to gain access to the ore body. Simultaneously a steeper tunnel driven from surface to an underground crusher station was put in to house a series of four conveyor belts which took the crushed ore from the underground storage bins under the crusher station and conveyed it to the surface.
Then it went to the mill ore storage bins. Ore from these surface bins fed the newly constructed ore processing plant or mill as it is known. 
This mill was capable of handling 4000 tonnes of ore per day. Once in the mill the ore was treated as it was in the 19th century but using modern equipment; it was further reduced in size, screened, washed and crushed to a fine powder. Each stage produced a separation of higher grade from waste material. The difference being that now none of these operations was done by hand, but by large electrically driven machines. The use of chemical reagents was also a 20th century innovation as flotation of the ore to cause the needed separation was aided by the addition of a variety of reagents, depending on the impurities which had to be separated from the copper concentrate.
To be continued….
Gold Frenzy, the story of Wicklow’s gold pt 6 – IMC Exploration
Gold Frenzy, the story of Wicklow’s gold – An excerpt from the book by Dr Peadar McArdle.
Dr McArdle, who recently retired as Director of the Geological Survey of Ireland, has had a long term interest in the history and origin of the Goldmine River gold deposits.
Text copyright Dr Peadar McArdle 2011.
Pt 6- Start of official gold mining operations.
The first technical report of the gold workings below the bridge at Ballinvalley was published by Abraham Mills Esq., manager of the Cronebane Copper Mines at Avoca, Thomas King and Thomas Weaver, in the prestigious Philosophical Transactions of the Royal Society of London for the year 1796 and subsequently reprinted in the Transactions of the Dublin Society for 1801. The account describes the extent of the workings and the nature of the bedrock and overburden of Croghan Kinshelagh and its ravines. Particular attention was paid to the distribution of quartz veins, all of which were reported as barren of gold.
Operations were started on 12 August 1796 and it is reported that a gold particle was recovered on that very day. Thomas Weaver, as one of three Commissioners (including Abraham Mills) appointed to manager the venture, was a key figure and he would in time gain a considerable reputation as a geologist. However at this time he was a relatively recent graduate of the University of Freiburg, aged only 23, and he had been in charge of the copper mines at Cronebane and Tigroney since 1793. The Goldmines Act received the Royal Assent in April 1797 and the first ingot of gold was sold to the Bank of Ireland two months later. The purpose of the operation, according to G.A. Kinahan, was “endeavour to collect all the gold deposited, and thereby to remove every temptation for the assembling of mobs, whose numbers had before that time increased to a very alarming degree.” A most noble motivation! There was no question that the Government, whether British or not, might be interested in any gold recovered!
The workings were carried out efficiently and thoroughly, using riffles and similar equipment. However in Cornwall, the tin ore was not confined to linear stream courses nor was it covered by barren subsoil. Instead it was scattered throughout granite bedrock that, by means of chemical alteration, now had the appearance of soft disaggregated subsoil from which the durable pieces of ore could be easily washed. In Goldmine River the gold was preferentially found to occur at the base of the subsoil (as Camden had originally reported to London) and so the overburden right down to bedrock was thoroughly worked and all gold particles extracted. Only when the overburden exceeded 9 metres in thickness did this not happen. By the time of the May 1798 Rebellion, when the workings ceased, another 17 kg gold had been profitably recovered. A decent amount of production but nothing compared with the 80kg recovered by the neighbours in just six weeks. Weaver states in 1819. “Government had fully reimbursed its advances, the produce of the undertaking having defrayed its own expenses, and left a surplus in hand.”
A party of militia went to the workings at the end of May 1798, when the disaffected workforce had apparently gone off to join the rebels, and transported all the timber and materials back to Rathdrum where they were used in fitting out a barracks. The militia were only just in time, for shortly afterwards the rebels arrived and destroyed any buildings or workings remaining at Goldmine River. The Commissioners of the company served as military officers themselves and were rewarded by the company when the rebellion ended, with First Lt Weaver receiving silver plate worth30 guineas, a handsome reward.
To be continued…
Other books by Dr Peadar McArdle can be viewed on Amazon here