Buddle pit

A buddle pit or buddle pond is a pit, often circular when specifically constructed, the purpose of which was to separate by sedimentation minerals from lighter rock dust in crushed ore, and used in the mineral mining industry (such as in extracting tin, lead and zinc). Many of the relics seen today date from Victorian times.

Early examples of buddle pits were often natural hollows in the ground, adapted by lining them with stone or clay to make them waterproof.

A purpose-built pit, constructed from stone or brick, cement and mortar, contained water, and a set of brushes, often powered by a water wheel, which rotated in the water in order to agitate the mixture, the result of which was that the heavier and denser material - i.e. the ore - tended to collect at the centre of the pit, from where it could be retrieved. The worthless gangue was then disposed of, often by draining.

Usually a set of buddle pits was utilised, with the richer central deposits in the pit being carried to another buddle, where they were treated in the same manner, and so on.

Whilst the round buddle pit was the most common, there was a variation called the concave buddle, which had a concave bottom.

The following detailed extract comes from Machinery for Metalliferous Mines: A practical treatise for mining engineers, metallurgists and managers of mines, by E. Henry Davies, C. Lockwood and son, 1902 :

The concentrating machine for slimes, which has hitherto been a great favourite, is the round buddle, and this was perhaps due to the great simplicity of its construction, which permitted its being made out of the odds and ends of machinery usually to be found on a mine. The fixed and revolving cast-iron heads, shafting, bevel wheels, and driving pulleys, are usually procured from a firm of machinery makers.

The buddle itself consists of a shallow circular pit formed in the ground from 14 ft. to 22 ft. diameter, and from 1 ft. to 1½ ft. deep. The poorer the slimes the greater the diameter, and as the product from the buddle always requires re-treatment, it is usual to concentrate first in a machine of small diameter, and then to re-treat the concentrates thus produced in one of a larger diameter. The sides of the buddle pit are formed of stone or brick, set in mortar, and the floor, which has an inclination outwards of 1 in 30, is made either of smooth planed boards or cement run upon a layer of concrete. The centre head is from 6 ft. to 10 ft. in diameter, and may even be less. A revolving head is fixed to the shaft, and this carries four arms. The revolving head receives the slime waters from the trough, and distributes them on an even layer over the fixed head ; the liquid stream, which should be in a uniform thin film, falls over the edge of the fixed head, and distributes itself outwards over the sloping floor of the buddle towards the circumference, depositing in its passage the rich ore it contains, according to its specific gravity, the richest first, close to the fixed head, and the poorest at the circumference. To each of the four arms a board is attached, carrying a cloth or a series of brushes, which sweep round and smooth out each successive layer of mineral as soon as it is formed. In some cases sprays of fresh water are used instead of the cloths or brushes, the number of revolutions in either case being 3 or 4 per minute.

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