Twenty years after Brenton Symons published his map of the Liskeard mining district he wrote this description of the Caradon District within his sketch of the geology of Cornwall.
A sketch of the Geology of Cornwall
By Brenton Symons, F.C.S., Assoc. Mem.Inst. C.E. Mining engineer and metallurgist
The barren aspect of the Bodmin Moor is reflected its rocks, which are very destitute of metallic ores, and it is only on the southern fringe of the granite that copper and tin ores abound. At Roughtor, east of Camelford a large sum was expended to discover whether the tin veins in granite improved with depth, but the failure was complete. At Blisland where there is a well marked, though very granitic group of elvans, no lodes of any promise have yet been noticed, but no exploration of importance have been made.
The mines around Caradon Hill- 1208 feet high-were originated by some miners driving an adit in 1836, but though comparatively modern, after a brilliant existence the first fruits of the district have been gathered, and the mines once so numerous and prosperous are now mostly stopped. South Caradon, the first mine opened, yielded 9% ore, and gave for many years handsome dividends, the total profit having being £380,000. The copper group extends eastward through East Caradon to Glasgow Caradon both very profitable mines. To the north is the Phoenix group of tin veins, where owing to the projections of granite ridges, and the faulting of the lodes, the hanging wall is slate, whilst the foot wall is often granite. The matrix of the tin ore is composed of quartz, chlorite and earthy iron ore. Adjacent the surface, copper pyrites and malachite are found. Nearly all the lodes dip steeply towards the granite, and have average width of rather more than three feet. At Gonemena tin ore is found in a manner somewhat resembling Carclaze, the excavation is a third of a mile long, and occupies a dozen acres, but the depth is only fifty feet.
To the west, the lodes are principally tin producing, and continue with a group of elvans through St. Neot to Warleggan. Though the mines have only been worked in a partial and desultory way, there is ample evidence that good tin lodes, which merit exploration, exist. At a mine called Tin Hill a large quantity of stream tin was obtained from a remarkable deposit of gravel and boulders beneath cliffy granite. Some elvan courses have been worked for tin with moderate success in this district.