A somewhat similar bowl-shaped concentrator is known as the KNUDSEN BOWL.ĪIRPLANE DRILL A compact, engine-powered placer drill designed for use in areas of difficult access. Tailings overflow the rim while gold and other heavy minerals are retained by the riffles. Feed entering at the center is carried upward and outward by the flow of water and centrifugal force. It consists essentially of a bowl-shaped vessel, rotated about its vertical axis and provided with circular riffles. See - Indicated value.ĪINLAY BOWL A wet, gravity concentrator used for the recovery of gold and other heavy minerals from alluvial materials. To be valid, such adjustments must be based on careful diagnosis of sampling problems, and must reflect sound judgement. In placer drilling, the adjusted value is also known as a CORRECTED VALUE. See - Skim bar.ĪDJUSTED VALUE A sample value that has been increased or decreased by an amount deemed necessary to offset known variables or other factors that may cause discrepancies in the initially indicated value. Accretion bars are typically formed along the short, or inside radius of curves. Skip to: Placer Terms F-N Placer Terms O-ZĪCCRETION BAR A low-level deposit of sand and gravel formed in a stream by gradual addition of new material. Fay, Albert H., A Glossary of the Mining and Mineral Industry. In Eighth Report of the (Calif.) State Mineralogist, pp. Dunn, Russell 1., Drift Mining in California. H., The Gold Placers of Parts of Seward Peninsula, Alaska. Prepared under the direction of the American Geological Institute. Names in parentheses refer to sources as follows:ĪGI. It should also be noted that the definitions given here are intended to be descriptive rather than legal, and they should be used accordingly. But in placer mining, the term FLOTATION is applied to the minimum water depth needed to move an operating dredge. For example: The term FLOTATION, as used in the general mining industry, relates to a mineral separation process. On the other hand some are unique to the placer industry or at least they have placer-related meanings different from those in general use. Many of the following terms have universal definitions, that is, they have definitions common to all branches of the mineral industry.
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