Materials Management Practices

Ore: A natural mineral deposit containing economically recoverable amounts of one or more metals. Ore is mined, crushed and sent directly to the mill for concentrating of the valuable metal it contains. Alternatively, ores containing leachable minerals may be sprayed with dilute sulfuric acid to recover those metals, over a period of time. The process is conducted in an environmentally sound manner by ensuring capture of metal-bearing solutions.

Overburden: Any material (i.e. topsoil, dirt, rock) that must be removed to reach the orebody is called overburden. Overburden generally lacks any recoverable minerals and contains only trace amounts of metals.

Waste Rock: Naturally occurring rock which has been mined but is not of sufficient value to warrant further processing. This rock is usually separated from the ore body and set aside in another part of the mine. Waste rock may be used for road construction at the mine site. If TRI reporting requirements are triggered at a facility, metals contained in that portion of the rock which is set aside on the property and not further processed must be reported as a "release to land."

Tailings: The portion of washed or milled ore that remains after metal-bearing minerals have been removed in the flotation process. In this process ore is ground to a fine sand consistency, mixed with water and biodegradable reagents to create a slurry that is piped into flotation tanks where it is agitated with air causing a froth. The metallic minerals adhere to the froth and float to the top of the tanks and are skimmed off. The remaining material, referred to as tailings, sinks to the bottom and is removed.

Tailings, having the consistency of fine sand, contain trace amounts of minerals which cannot be recovered in the process. Tailings are placed into on-site impoundments behind engineered earth and rock dams to confine the storage of this material in a controlled area. At some facilities tailings are partially dewatered prior to placement in the impoundment, thereby improving stability of the tailings. Tailings impoundments are generally monitored for seepage as well as structural soundness.

Some of the water is removed for reuse from the tailings so that the material is stabilized for long-term storage. The stabilized tailings are eventually planted with grass, trees, and other vegetation or are capped to prevent windblown emissions. Although their impact on the environment is limited, metals in impounded tailings are required by the TRI program to be reported as a "release to land."

Slag: A by-product of the smelting of copper and lead consisting largely of iron oxide, calcium oxide and silica. Slag contains low concentrations of metals in a fused, glassy form with the appearance of hardened lava. Slag is skimmed in a molten state and deposited at a designated slag management area at the smelter site. Because the slag is managed without co-mingling with municipal wastes organic acids are not generated and associated leaching of metals is avoided.