A Fatal First Crushing

 

In 1878 Government Surveyor Charles Sprent's spruiking of 'beds of iron conglomerate something resembling the famous “brown face" of Mount Bishcoff' in Tasmania's Mount Heemskirk region led to a rush to exploit the untapped potential of the region.

When tin mining began in Tasmania in the 1870s, Cornwall had been the centre of English tin mining for about 3000 years and by the eighteenth century, Cornishmen were firmly established as the world's pre-eminent hard rock miners. During the mid-to-late nineteenth century, Cornish mining expertise spread across the world including to Tasmania where the local mining community chose to rely on the 'intuitive' Cornish mining knowledge rather than local geological investigations.

At Heemskirk, the allure of a Cornish “practical miner" was too alluring for Hobart-based British Lion Prospecting Association which floated the Carn Brea Tin Mining Company and appointed Josiah Thomas (JT) Rabling as manager in January 1883.

Section of waterwheel

All the 1880s mines on the Heemskirk tin field, including Carn Brea, followed the practical and economical Cornish method of water-powered mining. A typical set-up consisted of running water from a stream to turn a waterwheel. A drive belt connected the waterwheel to the camshaft of a stamper battery, raising and dropping the heavy rods to crush the tin-bearing rock. At Carn Brea it is still possible to see the stamper and waterwheel, along with the adit (mining tunnel), dam site, water race, and wheel pit, making it a rare demonstration of the simple technology of generating power from water to drive a crushing plant.

The first half-yearly meeting of the Mining Company in Hobart in July 1883 glowed with happy anticipation. Neither the £1800 advance on machinery, nor the six calls on shares, had disturbed the shareholders' equanimity. Ore said to contain a payable 7.5 to 14 per cent of tin had been paddocked awaiting the crusher.

The stamper battery

The Carn Brea was one of nine mines on the Heemskirk field to erect a stamper battery for crushing. By October 1883, one of those mines, the Orient, was ready to crush, but it was not long after that the Launceston Examiner was reporting that the low yield of tin was 'a great damper … on tin mining at Mount Heemskirk'.

Unperturbed, the Carn Brea Tin Mining Company kept going until at least its second half-yearly meeting in March 1884. At that meeting it was revealed that although the results of the first shipment of 30 bags of crushed ore were not yet available, directors regarded the mining operation as a failure. Work had been suspended and many shares in the company had been forfeited. It was not long after that work seems to have been abandoned and Rabling appears to have left Tasmania.

The failure of the Carn Brea Tin Mine and the failure of the Heemskirk tin field it was part of appears to have been the result of rich patches of detrital cassiterite being mistaken for large ore bodies like those which were paying dividends at Mount Bischoff. The disaster led the Assistant Government Geologist George A Waller to comment in 1902 that 'in some cases it is impossible to avoid the conclusion that the managers did not know tin ore when they saw it'.

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