Heap Leaching Gold & Silver Ores
An investigation of a particle agglomeration technique as a means of increasing the percolation rate of leaching solutions through heaps of clayey or finely crushed, low-grade, gold and silver ores. Bench-scale and pilot-scale experiments conducted on different ores indicated that the percolation rate of cyanide leaching solution was enhanced markedly by mixing the ore with […]
Gold Heap Leaching Practices
Heap leach gold recovery techniques are employed at Ortiz. Caustic cyanide solutions are sprayed onto crushed rock piles, dissolving the metallic gold from within the rocks and carrying it out as a ‘pregnant’ gold containing solution. The solution is then passed over carbon particles which the gold preferentially precipitates upon. The gold loaded carbon is […]
Sample Preparation for Gold & Silver Assay
Sample Preparation: Aqua regia with, occasionally, the addition of hydrofluoric acid is the most used lixiviant, and is applicable to most ore types. Other combinations of acids as well as cyanides are also used, and pre-roasting is sometimes applied. Digestion time and amount of reagent vary, quite naturally, with the amount of acid consuming materials […]
Foam for Dust Control
The Code of Federal Regulations (Title 30, Chapter 1, Part 57, Section 57.5-1) requires that metal and nonmetal mines shall maintain a time weighted average (TWA) for total and respirable airborne dust concentrations below that established by the American Conference of Governmental Industrial Hygienists in 1973. This TWA for total dust concentrations must be under […]
Carnallite & Sylvinite Ore – Potash Flotation
The mission of the Bureau of Mines minerals research program is to help improve minerals processing technology so that the Nation’s mineral needs can be fulfilled in a manner that reduces waste and ensures that minerals and metals are processed, used, and recycled at acceptable economic, social, and environmental costs. In accordance with this mission, […]
Fire Resistance of Conveyor Belts
Conveyor belt fires can present a serious hazard in the confined environment of an underground coal mine. To minimize this hazard, Federal regulations were enacted following the Federal Coal Mine Health and Safety Act of 1969 to require the use of acceptable fire-resistant conveyor belts and suitable belt slippage-sequence switches, fire warning devices, and fire […]
Uranium Acid Leaching
Mechanism of Uranium Leaching: Uranium leaching with sulphuric acid is a complex process governed by chemical dissolution, and the oxidation of uranium. It is controlled by surface etching, diffusion, and mass transfer within the ore. The physical parameters are in turn controlled by the physical properties of ore, and the ore size. The leaching process may […]
Thiourea Gold Leaching
The use of thiourea, (CS(NH2)2 as a complexing/extracting agent for gold and other precious metals has shown promise for implementation in the mining/metals industry. Laboratory testing of this reagent has indicated that a thiourea process for gold extraction has several advantages over conventional processing techniques. The use of cyanide for the extraction of gold from […]
Zinc Chloride & Electrowinning
To help assure an ample domestic supply of zinc and other essential minerals which provide the foundation of the Nation’s economy and security, the Bureau of Mines is investigating an aqueous chlorine-oxygen leaching procedure to produce zinc chloride from complex sulfide concentrates and is also studying methods of fused-salt electrolysis to produce special-high-grade zinc metal […]
Nickel & Cobalt Electrowinning
As part of the goal to develop technology that can meet critical and strategic needs of minerals and metals, the Bureau of Mines is investigating a procedure for selectively extracting nickel, cobalt, and copper from low-grade domestic laterites. Although the Nation produces less than 10 pct of the primary nickel it consumes and essentially none […]