Small Mining

Dredging

In recent years diving enthusiasts have taken up small-scale placering as a profitable venture.

Various kinds of apparel and equipment are used, but the investment is usually not more than few thousands dollars. Wet suits and canvas shoes are almost a necessity for entering cold mountain streams to search the streambed for pockets that might contain gold. Beginners should be equipped with a snorkel, a face mask, gloves, a weighted belt, fins, a gold pan, and a crevicing tool. More experienced divers may use the popular scuba equipment, but this calls for special knowledge to insure safety. Crevicing tools include large spoons, tire irons, crowbars, etc.--almost anything that can reach into tight places and dislodge nuggets from the stream bottom. The pan should be used to test sands from various places where gold would be expected to settle, such as the downstream sides of obstructions. Where colors in the pan indicate a favourable area of the stream, a more intense search may be made.

Small dredge with gravel pump
Small dredge with 5-inch gravel pump.

Mining equipment may include various combinations of pumps, miniature dredges, and riffle boxes that can be built from salvage by the operator or purchased from commercial sources. A number of manufacturers have produced special equipment for the purpose. One of the popular kinds is the jet dredge, a pipe-like device made of sheet metal curved at the intake end and with a water jet entry to propel the water and gravel through the straight portion. The jet is supplied from a portable pump and in effect causes gravel and sand to be sucked into and through the pipe. A riffle box built into the end section collects the gold and other heavy particles while the rest of the material discharges. The riffle box may be enclosed so it can function while submerged. Usually, a 6- to 10-horsepower pump is adequate; the hose to the jet may be 1-1/2 to 2 inches in diameter.

Manipulating the device underwater requires skill and patience, since the riffle section must be kept nearly horizontal during the mining operation. Floating platforms are sometimes used to support equipment. In this case, riffle boxes and other units may be installed on the platform. The usual operation includes moving many large boulders to get at the trapped gold underneath or alongside. Conventional equipment such as a rocker or a sluice may be employed to carry selected material from the streambed to a shoreline site for processing. Concentrates are then panned to recover the gold.

[ Small Mining - Rocker Dip box Long tom Sluice Surf washer Dreging Dry washer ]

From: Bureau of Mines Information Circular 8517 by J.M. West, released in 1971.

Rafal Swiecki, geological engineer email contact
January, 2007

This document is in the public domain.