The lodes worked occur in an area of clay-slates of Devonian age. Southwards towards Yelverton, these slates show signs of Metamorphism. Some 600-700 ft north of the workings is a large elvan dyke, which extends westwards to the Hingston Down-Gunnislake granite mass.
This article concerns four mines two of which were predominantly tin producers (Gem Mine and Walkham United) one predominantly copper, but also producing some tin (Sortridge Consols) and the last predominantly copper and lead, but also small amounts of tin (Walkham and Poldice Mine). All are situated close to the Walkham Valley on a west to east line between the 70 and 71 line of latitude. Of the four mines the only one to produce serious quantities of ore was Sortridge Consols. Production figures for Gem and Walkham United are small, but both have evidence of late medieval working for which records do not survive. Production figures for Walkham and Poldice are negligible. At all the mines the dressing floors are well preserved and worthy of investigation.
The mine is situated on the southern side of the Walkham River, just south of Grenofen Bridge. According to Dines there are two intersecting lodes, Lead Lode, coursing N 5° E and underlying 20° W and Copper Lode coursing about E 20° S and underlying 40° N. Adit level commencing 170 yds S. of Grenofen Bridge on Lead Lode and driven 100 fathoms S. and connecting with Engine shaft at 22 fathoms in and air shaft at 85 fathoms in. Engine shaft connects with four other levels, 14 fm, 26 fm, 38 fm and 50fm. Plans of the mine show minimal stoping, just a small stope each on the 26, 38 and 50 fm levels. The Copper Lode has driven upon at the 38 and 50 fm level for a distance of 38 fms west (Dines). Not surprisingly recorded output is minimal - 5 tons of lead, 25 tons of copper and 1 ton of black tin (Burt et al)
The history of the mine is complicated but it appears to have been part of the Huel Walkham sett which was in operation in the late 1850's and was working the Devon Poldice Mine also known as Old Poldice to the south east. In 1862 the Walkham and Poldice company was formed and it is this company that seems to have developed this northern part of the sett. The company was in operation until 1869. Walkham United Mine a later re-organisation of the same sett (and probably including Gem Mine) was in operation in the early 1880's (Newman).
Remains at the mine include a shaft and whim plat, 2 waterwheel pits and tin dressing floors.
This site and Gem Mine were worked much earlier than Walkham and Poldice. The early workings at Walkham United consist of two deep narrow openworks which traverse the slopes to the west of the mine. The date of these workings are not documented but are probably late medieval or earlier in origin. The earliest documented working of the mine dates to the early 19th century when it was known as East Poldice Mine. According to Lyson (1822) the mine was abandoned in 1815. In 1825 a leat is believed to have been cut to Poldice Mine so presumably it was being working again at this time (Dickinson). Further attempts to re-open the site is recorded in 1860 when men were exploring the old workings (PDWJ 5th Jan 1860). In 1861 the mine was known as Devon Poldice. The mine at this time is recorded as 20fms deep employing 20 persons (Williams). The mine plan from this period shows a leat, dressing floor, ancient workings and adit. During the 1860's Devon Poldice was incorporated into a new sett called Walkham and Poldice which included more land near Grenofen Bridge. The mine may have also been worked in conjunction with Virtuous Lady for a period in the 1870's (Newman). In 1881 a new company, Walkham United was formed to work the sett, which included Walkham and Poldice and possibly Gem Mine (Newman). The operation was short lived as the company was wound up in 1882. (TG 4th Aug 1882)
The mine worked three east-west lodes known as Main, Flat and North. Main Lode underlying 10° N has been worked opencast on the steep south-western bank of the River Walkham and by shafts, one at the eastern or lower end of the openwork and another to the west of it. Main lode is intersected below the openwork by Flat Lode dipping 45° N. Flat Lode and Main lode have been stoped to some extent for 50 fms west of the lower shaft. About 30 yds North of Main Lode and parallel in dip and strike is North Lode, which has shallow surface workings and two short adits driven westward into the higher part of the valley side. South of Main Lode there are surface indications of two trials, the most southerly being just west of the southern end of the viaduct (Dines).
Recorded outputs are 1860, 1861, 1867, 1873 and 1875, 24 tons of black tin and 50 tons of 6 per cent copper ore (Burt et al).
Remains include building foundations, a probable burning house, the walled dressing floor, two round buddles, a leat and the cast iron rising main within the shaft.
Two narrow deep parallel west-east openworks can be found on Furzeland Down, now woodland below Birchcleave House. These workings are not documented but are presumably late medieval or earlier in origin and appear to be an extension of the lodes at Walkham United. The first documented records of this mine date to 1822, when Lyson mentions a Wheal Grenofen within the parish of Whitchurch. This is believed to be the site of Gem Mine and was probably the first attempt to work the tin lodes below the earlier openworks. The mine was abandoned sometime between 1815 and 1822 (Lyson). In 1855 the mine was re-opened as West Sortridge Consols and was still named as such in 1859 (Newman). Recorded output from this time is 6 tons of tin valued at £323 (Burt et al). In 1871 the mine re-opened as Gem Mine and in 1873 was being worked by the Gem Tin Mining Company (Newman). The mine appears to have worked until 1874 during which time it produced 31 tons of black tin worth £2483 (Burt et al). In 1880 the mine was acquired by the Walkham Valley Tin Mining Company which in turn was absorbed into Walkham United in 1881.
Remains include adits, tramway, stamps wheelpit, hauling wheelpit, burning house, horse whim plat, leat, buddle wheelpit and dressing floors.
There are several lodes, but the mine chiefly exploited Main Lode, which courses nearly west-east and underlies 18° to 20° South. Sortridge Consols was on the western section of the lode and was not connected underground with the two Wheal Roberts to the east (North Robert and East Robert) which were operated together. Several other lodes of minor importance have been proved in the sett and developed to varying degrees (Dines).
Originally known as West Wheal Robert the mine was re-opened as Sortridge Consols in 1853 when a rich deposit of copper ore was found only 5ft from surface. In a matter of months £3200 worth of copper was sold for an outlay of £600. In 1854 the maximum depth was 30 fms with the lode as rich as ever. From the 20 to 40 fm level the course of ore returned over £50,000 (Hamilton Jenkin). At this depth the values showed a serious decline and the mine would have closed had it not been for an important discovery of ore in the two south lodes. As a result, an engine house was constructed and a 40" pumping engine installed. The mine continued in operation for at least another twelve years during which time the main shaft was carried down on the underlie to a depth of 152 fms. The mine was never as successful in this period of operation and the machinery was offered for sale in 1868. final closure appears to have taken place in 1871. The sale of machinery included the 40" pumping engine, a 22" winder and a 24ft waterwheel (Hamilton Jenkin). Output of copper ore from 1854 until closure is recorded as 7,792 tons worth £57963 (Burt et al)
In 1883 the mine was re-opened via the drainage adit to work low grade tin ore above adit level. The mine was subsequently worked until 1892. During this working pneumatic stamps were reputedly used, this being one of the first mine in which they were tried (Barclay). Interestingly Hamilton Jenkin states that the mine continued to be worked intermittently and in a small way until 1902. The output of black tin from 1883 until 1893 is recorded as 33.7 tons, worth £1794 (Burt et al).
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