AskDefine | Define hushing

User Contributed Dictionary

English

Noun

  1. The use of a heavy discharge of water to uncover a mineral vein or wash ore.

Verb

hushing
  1. present participle of hush

Extensive Definition

Hushing is an ancient mining method using a flood or torrent of water to reveal mineral veins. The method was applied in several ways, both in prospecting for ores, and for their exploitation. Mineral veins are often hidden below soil and sub-soil, which must be stripped away to discover the ore veins. A flood of water is very effective in moving soil as well as working the ore deposits when combined with other methods such as fire-setting. It was used widely from during the formation and expansion of the Roman Empire from the first century BC on to the end of the empire. It is now redundant except in a variant known as hydraulic mining, where jets or streams of water are used to break down deposits, especially of alluvial gold and alluvial tin.

History

The method is well described by Pliny the Elder in Book XXXIII of his Naturalis Historia from the first century AD. He distinguishes the use of the method for prospecting for ore and use during mining itself. It was used during the Roman period for hydraulic mining of alluvial gold deposits, and in opencast vein mining, for removal of rock debris, created by mechanical attack and fire-setting. He describes how tanks and reservoirs are built near the suspected veins, filled with water from an aqueduct, and the water suddenly released from a sluice-gate onto the hillside below, scouring the soil away to reveal the bedrock and any veins occurring there. The power behind a large release of water is very great, especially if it forms a single water wave, and is well known as a strong force in coastal erosion and river erosion. The method was most effective when used on steep ground such as the brow of a hill or mountain, the force of falling water lessening as the slope becomes smaller. If veins of ore were found using the method, then hushing could also remove the rock debris created when attacking the veins. Pliny also describes the way hillsides could be undermined, and then collapsed to release the ore-bearing material. The Romans developed the method into a sophisticated way of extracting large alluvial gold deposits such as those at Las Medulas in northern Spain, and for hard rock gold veins such as those at Dolaucothi in Wales. The development of the mine at Dolaucothi shows the versatility of the method in finding and then exploiting ore deposits.

References

  • Oliver Davies, Roman Mines in Europe, Clarendon Press (Oxford), 1935.
  • Jones G. D. B., I. J. Blakey, and E. C. F. MacPherson, Dolaucothi: the Roman aqueduct, Bulletin of the Board of Celtic Studies 19 (1960): 71-84 and plates III-V.
  • Lewis, P. R. and G. D. B. Jones, The Dolaucothi gold mines, I: the surface evidence, The Antiquaries Journal, 49, no. 2 (1969): 244-72.
  • Lewis, P. R. and G. D. B. Jones, Roman gold-mining in north-west Spain, Journal of Roman Studies 60 (1970): 169-85.
  • Lewis, P. R., The Ogofau Roman gold mines at Dolaucothi, The National Trust Year Book 1976-77 (1977).
  • Annels, A and Burnham, BC, The Dolaucothi Gold Mines, University of Wales, Cardiff, 3rd Ed (1995).
  • Hodge, A.T. (2001). Roman Aqueducts & Water Supply, 2nd ed. London: Duckworth.
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