Recovery and losses of tin at Giew Mill

Recovery and losses of tin at Giew Mill

by

The Cornish Sub-committee of the tin and tungsten research committee

NOTE.—This Report is published by the Institution of Mining and Metallurgy by request of the Tin and Tungsten Research Committee.

The reason for this particular investigation arose out of the more general inquiry into the methods of Cornish tin dressing with a view to their improvement. The conditions under which tin dressing is usually carried on in the county were carefully considered, and data sought, for establishing some sort of solid basis on which to build ideas of improvement. At the outset diligent inquiry showed that few people were agreed on the amount of tin lost.

The Committee therefore felt that data sufficient for forming a considerable judgment on the losses of tin did not exist. Records had in some cases been made over varying periods and under diverse conditions, but these only possessed a more or less empirical value, and in few cases had any claim to scientific correlation. While hoping later to make some use of these records, it seemed necessary to the Committee to start de novo and ascertain results from a mill in actual operation, and thus secure evidence which could be accepted as definite and precise.

Giew Mill, electrically driven, was chosen as affording an opportunity of investigating good modern milling practice, and because it was isolated from other mines so that the waters used for dressing purposes did not contain the effluent waters from other mines, and also because the ore was not complex.
The mill is situated three miles to the south-west of St.Ives, on the slope of Trink Hill, adjacent to Trencrom. It has been laid down on the natural slope of the hill, which gives plenty of drop for the various floors with little elevating, the slope of the hill being of sufficient length to allow stage after stage to follow in one continuous cascade. The calciner stands between the main dressing floors and the tin yard, making the passage of the concentrate easy, direct and necessitating no carting. All the concentrating machinery is under cover with the exception of a few dumb buddles treating tailings.

The Cornish Sub-Committee is composed of :

R. A. Thomas (Chairman), Manager of Dolcoath Mine, Ltd. Josiah Paull (Vice-Chairman), Manager of South Crofty Mine, Ltd. William Thomas, Manager of Tin croft Mine, Ltd. M. T. Taylor, Manager of East Pool and Agar Mine, Ltd. Arthur Richards, Managing Director of Cornwall Tailings Co. Ernest Terrell, Manager of Wheat Jewell, Marytavy. F. G. Cann, Manager of St. Ives Consols, Captain William Thomas (251 Co. Royal Defence Corps), Mining Engineer. S. Furze, Mill Superintendent at Giew Mine, St. Ives. H.Jenner, President of Royal Cornwall Polytechnic Society. T. Knowles, Principal of Camborne Mining School.

The Committee devoted considerable time to watching the operations at Giew Mill, and in view of the importance of the work and the need for undivided attention which they could not give, they engaged the services of a competent mining engineer, Mr. J. H. Rickard, who had had considerable experience in sampling in various parts of the world.”

The complete report is nearly ten times the length of this extract and contains a great deal of detail which indicates how methodical the investigation was and how well it met its objective.

It will also be noted that the Sub-Committee had expanded considerably from that named at the Meeting in 1915.

The follow-up paper by Mr S Furze presented at a General Meeting on 24th January, 1920 gave detailed information on the construction and operation of the Californian Stamps and screens manufactured by J & F Pool of Hayle, the Tube Mill made by Francis & Chalmers and used to grind middlings from the Buss tables.
The Research Committee report occupied about ten pages of the Transactions, Mr Furze’s paper took up 19 pages and the report on the discussion which followed took 10 pages. This demonstrates the high level of interest in the subject.

In spite of this there is no mention of any immediate follow up and the next report of any action was two years later when a Council meeting on 31st Jan 1922 considered a letter from Mr L A Hards suggesting that arrangements should be made to obtain an expression of opinion from the members concerning the conditions of the mining industry in the Camborne – Redruth area and the best means of helping towards resucitation. It was decided to arrrange a General meeting on 18th Feb for a discussion introduced by the President  on “The advantages and disadvantages of a comprehensive scheme for resucitating the mining industry in the Camborne – Redruth district especially within the area yielding complex ores of tin, copper, arsenic and wolfram”.

The following is an extract from the notice of meeting issued to Members on February 7th, 1922 :-
The subject to be discussed being of unusual importance, longer notice than usual is given of the meeting. We are instructed by the Council to state that your attendance is specially requested, and that it is particularly desired that Members should express their views at the meeting, or in writing if preferred, on the questions appended”

The questions were :—
1.— Is a larger scheme of operations than any hitherto attempted for the area practicable ?

2.— Is it more advantageous to operate the area under a single control or to work different properties under separate managements ?

3.– Can drainage be most economically and efficiently accomplished by means of a central pumping plant ?

4.— Are conditions suitable for treating the output at a central milling and ore-dressing station ?

The President, at the General Meeting on February 18th, 1922, introduced the subject for discussion. At this meeting the views of absent members, which had been received in writing, were read and followed by a long discussion which was adjourned to March 4th, when the following resolution was passed unanimously :—

“That the Members of the Cornish Institute of Engineers, having considered the general question of mining in the Camborne – Redruth area, are of the opinion that the geological evidences relating to the lodes still further north than the Main Lode Series, which have been extensively worked, present ample justification for the expenditure necessary to prove such lodes; and, that the Council be requested to take such action as they deem advisable to support a comprehensive scheme for resuscitating the mining industry in the Camborne – Redruth district, especially within the northern area yielding complex ores of tin, copper, arsenic and wolfram.”

At the next Council meeting on 31th March 1922 it was agreed:-
That the consolidation of Dolcoath, South Crofty and East Pool and Agar interest is desirable and, if effective would prove to be generally advantageous to the mining interests of the whole district. That the Western Section of the northern ground, namely the section including the Roskears and Setons covers a sufficiently comprehensive area to justify mining operations.

The President was requested to proceed with preparation of a scheme of operations for the area defined in decisions (2) and that Members be asked to forward any information which would be of assistance.

On the 27th of April 1922 at a Council meeting the President read his scheme for resucitating mining in the Northern area of the Camborne – Redruth district. The Council unanimously approved the scheme presented by the President and considered it to be sufficiently explicit to be forwarded to his principals. Council also agreed that a sub-committee should be formed to confer with President’s principals in the event of their coming to Cornwall and that the valuable information should eventually be preserved in the “Transactions”.