THE MINING AND SMELTING MAGAZINE

VOLUME 2. 1862

 WHEAL MARY ANN

    This mine is worked to the south of, and on the same lode as, Wheal Trelawney, in the parish of Menheniot, in the general position I have already described. Taken together with Trehane (now in Trelawney sett) these mines have, next to East Wheal Rose, probably afforded the most productive piece of lead ground in the county; and even at present, at a depth of upwards of 200 fathoms from the surface, the lode is nearly as productive as ever, although the expenses having increased with the depth, the profits now form but a small proportion of the value of the produce. The general bearing of the lode is from 20º to 25º W. of S, with an average underlie east of about 15 inches in a fathom. The extent of the workings are sufficiently shown in the section (Fig,2) by which it will be seen that at the deepest point - the bottom of Clymo’s Engine-shaft - the workings extend to the nominal depth of 186 fathoms below adit, or 216 fathoms below the surface. I say nominal depth, because the real depth is probably fully 10 fathoms deeper, inasmuch as many of the levels are nearly 11 fathoms apart. In the northern part of the sett, adjoining Trelawney boundary, about Barratt’s shaft, the ore made up to grass, all the levels above the 140 inclusive are either communicated to that mine or are close up to the boundary. Southwards the lode is cut off in the lower levels by the slidy ground which I shall refer to bye and bye, but in this part it does not “back up” at all, and is not traceable shallow: behaving, in this respect, like the Herodsfoot lode going south. Of the three shafts, Barratt’s is sunk on the course of the lode, but Pollard’s and Clymo’s are vertical all the way. Speaking generally, all the ore ground, with the exception of some arches and low quality ground, which will come away on high tribute, is gone above the 150. Above this level there are certainly twenty-one pitches working, but they are all at a high tribute - averaging £13 per ton. The substantial ore ground is entirely in the bottom of the mine, below the 150, and it is all working by stopes - of which there are about twenty - with the exception of a few arches of ground that are being taken away by two pares (a man and a boy each) at £12, tribute on either side of Pollard’s below the 150. Consequently it will suffice for us to consider the levels blow the 150 - viz, the 160 and 172. The 160 is communicated, from shaft to shaft (between which the ground is all gone) and is besides driven considerably north and south of Pollard’s and Clymo’s respectively. The 160 south of Clymo’s is extended about 75 fathoms from cross-cut from shaft, and is now being driven by six men at £3 - 10s., in a lode worth 8 cwt. per fathom. For the whole of this distance the lode has been orey, averaging probably from 5 to 7 cwt. per fathom - but at some points reaching as high as 20 cwt., and at others falling as low as 2 or 3 cwt. Behind the ground which has gone and that still standing as well as the stopes working is 5 fathoms of whole ground. In the 13 fathoms following this there are two stopes, worth 6 cwt. per fathom, working by four men each at £1.50 and £1.75 respectively, but which, however, are not beaten away more than 1 fathom up. In the 22 fathoms succeeding this three other stopes are working, worth 6 cwt. per fathom, one by six men and two by four men each: the lode in this run of stopes is large, being fully 5 feet wide, composed of fluor-spar (“can”) interspersed with lead, with a band of calc-spar, of ribboned structure on the west wall. Between this and the shaft the ground is gone to the 150. The 160 north of Pollard’s is extended about 92 fathoms north of that shaft, to within 55 fathoms of Trelawney boundary, and is now driving by four men at £10 per fathom in a lode 2 feet wide, producing 3 cwt. of lead per fathom. For the first 30 fathoms from the cross-cut the lode is beaten away to the 150; but for 13 fathoms back from the end ground is whole. Between these there is 49 fathoms of ground in course of taking away in four stopes of four men each, worth on an average of 5 cwt. per fathom: these are worked up on the whole about 7 fathoms from the level. The 172 from Pollard’s and the 175 from Clymo’s are within 30 fathoms of being communicated, and this expected to be accomplished within the year. At Clymo’s the lode has not long been intersected in the cross-cut, only 4 fathoms each way having been opened on it, which, however, has been entirely through orey ground. The 175 south is driving by six men at £31.50 per fathom, in a lode from 6 to 8 feet wide worth £6 to £7 per fathom. The present end is not so good as it has been, the lode being disturbed by a slide which has been seen in the upper levels and dips north. The bearing of the lode in this end is out of its normal direction, being nearly north and south. The 175 north is also driving by six men at £3.50 , in a good lode worth 7 cwt. per fathom, in a pretty killas. The lode in this end has its normal bearing of S. 20 W. A winze is sinking below the 160 to come down on the 175 south: it is now down about 9 fathoms, and is 8 feet ahead of the end. The lode in this winze for the whole depth has averaged 6 cwt. per fathom. The 172 south from Pollard’s is extended about 35 fathoms south of cross-cut from shaft, now driving by six men at £14 - in the killas by the side of the lode, the latter being still harder, consisting of 1½ feet wide of “capels” and 1 foot of flour-spa with a little carbonate of lime. For the first 25 fathoms south of Pollard’s this level passes through a lode worth on an average 2 tons to the fathom, which has gone down in the bottom: the last 10 fathoms have not been so good - varying from 10 cwt. to 15 cwt., and averaging probably 12 cwt. About 30 fathoms from the cross-cut from shaft, and 5 fathoms back from the end, a winze has been communicated from the 160; and between this winze and the cross-cut there are five stopes working by twenty-four men at a mean of £4 per fathom, on a lode producing 6 cwt. On an average these stopes are worked up 5 fathoms from the level, but as there is really 12 fathoms of ground between the two levels, there is still 7 fathoms standing. This level is being driven dead, while the 170 from Clymo’s will have a rise of 3 fathoms, so that the water may all flow to that shaft. The 172 north of Pollard’s is extended 25 fathoms from the shaft, and now driving by six men at £14 - in a lode 4 feet wide composed of carbonate of lime and fluor-spar worth 6 cwt. per fathom, with 2 feet of “capels” on the west side. For this length of 25 fathoms the first 15 fathoms from the cross-cut will yield on an average 10 cwt. per fathom, and the last 10 fathoms to the end, about 6 cwt. In this distance three stopes are working: one 712 fathoms long from cross-cut, by four men at £4.50 per fathom, up 6 fathoms; another, 6 fathoms long, by six men at £4, up 3 fathoms; and a third, just pitched, by four men £4.50. These three stopes average about 6 cwt. Clymo’s shaft is at present sinking by twelve men at £28 per fathom, and is down 11 fathoms. In the bottom of this shaft there are two 8-inch buckets lifting the water to the 160, at which level it flows back to Pollard’s. In this latter shaft there is one 8-inch bucket, and two 9-inch poles which raise the water by a “shammel” lift to the 110, where it goes back again to Clymo’s: from the 110 at Clymo’s it is brought to the surface by four 13-inch poles. When the 172 is communicated, all the lifts in Pollard’s will be done away with, and the drainage of the mine effected entirely through Clymo’s. The present engine at Pollard’s - a 46-inch - will then be done away with, for the engine on Clymo’s shaft - a comparatively new 80-inch - has ample power to put the mine considerably deeper. This Clymo’s engine, which is one put up by Mr. West, of St. Blazey, is among the finest in the county, and is kept in splendid order; but as yet it has done very little work, although it has been erected eight years. There are double skip roads in both shafts. This lode, which here and in Trelawney has certainly been remarkable for its productiveness, is a large and strong one containing a great deal of fluor-spar and carbonate of lime - with capels generally on both sides, varying from 1 foot to 6 feet wide. No productive parallel lodes have been met with - indeed no cross-cuts have been driven in Mary Ann Sett - but trials have been ineffectually made Trelawney and Trehane. One of the most remarkable features, however, in Wheal Mary Ann remains to be noticed - and that is the great run of “slidy” ground, which cuts off the lode southward, dipping south. Altogether it is very similar to the broken ground already described in Herodsfoot, although it seems to be wider, for as yet, unfortunately, it has not been got through in Mary Ann sett although an extensive trial has been made to this effect at the 110 fathom level. The first effect on the lode of the approach of this slidy ground is that, it is thrown to the right, with a bearing W. 45 S. After the slidy ground is intersected, the lode has not been again seen, although the 110 has been driven considerably south and also east and west. Some branches were more than once met with, but they soon disappeared again, and at present the trial is for the moment suspended. The importance, in the interest of the future of Mary Ann, of a discovery in this direction is too obvious to need pointing out. This mine would then be in the position of Herodsfoot - having only to drive up deep levels into a new mine, for although the present limits of the sett south is the boundary, any required extent of ground can be readily had further south towards the village of Menheniot. Wheal Mary Ann has now been working sixteen years last May, and during that time she has made splendid returns and excellent profits. The present returns are about 60 ton per month of best ore and 25 tons of seconds - the former worth about £25 and the latter £10 per ton. But when a mine - and particularly a lead mine - has to continue sinking pretty smartly to keep them up, profits generally become “small by degrees and beautifully less.” With the present excellent management the bottoms may continue to be worked with profits for some years longer, but expenses must gradually increase, and profits diminish in a like ratio. The great future of this mine would be a discovery south, which would give it a new start. It is difficult to form an opinion as to the probability of such a discovery being made, but there are certainly fair chances. This mine is under the management of Mr. Peter Clymo, of Liskeard, the manager of South Caradon, and also until recently the manager of Trelawney. The agents are Captain Henry Hodge (managing), and Captains Joseph Harris and James Stephens. Besides the two pumping engines mentioned, there is a 24-inch double whim engine drawing from both shafts; a 22-inch horizontal engine for crushing and stamping; and six water wheels worked by the water pumped from underground.