grease table, noun phrase

Origin:
See quotation 1931.
Diamond-mining
A sorting device in which a greased surface is used to retain the diamonds. See also sorting table (sorting sense 1 b).
1931 G. Beet Grand Old Days 99After a process of jigging, the final concentrates are made to pass over shaking grease-tables to which the diamonds adhere, while the other minerals are automatically washed away, the separation being based on the well-known affinity of the diamond for grease (petroleum jelly).
1946 S. Cloete Afr. Portraits 129A careless overseer..spilt some grease on a table and it was found that diamonds stuck to the grease, allowing other pebbles to be washed past irrespective of their specific gravity.
1967 E. Rosenthal Encycl. of Sn Afr. 222Grease Tables,..The apparatus was built by George Labram..and F.B. Kirsten at Kimberley and patented in 1897. De Beers Consolidated Mines used it under royalty, but ultimately bought it outright.
1973 A. Hocking Diamonds 15The concentrate less than 3 mm across goes over electro-magnetic vibrating screens which remove all water, then gravitate down to the grease tables. These have sloping, three-stepped decks which are vibrated as the concentrate steadily passes over them.
1977 S. Afr. Panorama Aug. 16Syndicates began to be formed so that diggers could pool their resources and buy wims and traction engines, crushers and grease tables.
1978 E.L. Williams in Optima Vol.27 No.4, 103The long process is completed with concentrates from the desert plants arriving..for final concentration and the harvest of diamonds, up to 5000 carats a day, by X-ray separator, a technique now used..in place of the historic grease tables and belts employed for so many years.
1990 B. Steyn in S. Afr. Panorama Jan.Feb. 71 (caption)The grease tables where the final recovery of the precious gems takes place.
A sorting device in which a greased surface is used to retain the diamonds.
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19311990