Elutriator design manual for coarse heavy mineral recovery from sluice box concentrate

Abstract

This manual addresses the design and fabrication of an elutriation system for the separation of coarse heavy minerals from waste rock. Elutriation is a process for separating a mixture of minerals into two or more products and utilizes the difference in settling velocity between particles to effect this separation. An upward flow of water runs countercurrent to the material flow in a hollow elutriation column. Particle separation is affected by particle density, size and shape and the upward water velocity. It was felt that the design and demonstration of a low cost, functional and efficient unit for the concentration of coarse, heavy minerals would be of benefit to the placer mining industry. Industrial efficiency can be improved by the additional recovery of byproduct heavy minerals with market potential. Elutriation provides an inexpensive method for processing +1/4 inch, sluice box concentrate to recover by-product heavy minerals. Elutriator design emphasized the use of materials which are inexpensive and readily available to the average placer gold mining company. The design also incorporated concentrate storage and shipment functionality into a detachable section of the elutriator. Design is based on the construction of a prototype unit and testing of the unit for coarse cassiterite (Sn02) recovery efficiency. Laboratory testing utilized 3/4" x 3/16" sluice box concentrate from Shoreham Resources Ltd's Cache Creek Mine, Tofty, Alaska. Following laboratory testing, the elutriator was field tested on-site in September, 1990. Both laboratory and field testing were highly successful. The elutriator proved to be a simple, robust concentrator for this application and produced tin recoveries and grades in excess of 99% and 55% respectively. Field feed grades to the elutriation unit were approximately 26% tin.