Taconite - A highly abrasive iron ore. Tailings - Material rejected from a mill after most of the recoverable valuable minerals have been extracted. Tailings pond - A low-lying depression used to confine tailings, the prime function of which is to allow enough time for heavy metals to settle out or for cyanide to be destroyed before water is discharged into the local watershed. Talus - A heap of broken, coarse rock found at the base of a cliff or mountain. Telluride - A chemical compound consisting of the element tellurium and another element, often gold or silver, Thermal coal - Coal burned to generate the steam that drives turbines to generate electricity. Thickener - A large, round tank used in milling operations to separate solids from liquids; clear fluid over flows from the tank and rock particles sink to the bottom. Tonnes-per-vertical-meter - Common unit used to describe the amount of ore in a deposit; ore length is multiplied by the width and divided by the appropriate rock factor to give the amount of ore for each vertical meter of depth. Trading floor - the area of a stock exchange building where shares are bought and sold. Trading post - An area on the trading floor of a stock exchange where current stock prices are listed and where the floor traders (representatives of brokerage firms) meet to buy or sell the stocks listed at that particular post. Tram - To haul cars of ore or waste in a mine. Treasury shares - The unissued shares in a company’s treasury. Trench - A long, narrow excavation dug through overburden, or blasted out of rock, to expose a vein or ore structure. Trend - The direction, in the horizontal plane, of a linear geological feature, such as an ore zone, measured from true north. Tube mill - An apparatus consisting of a revolving cylinder about half-filled with steel rods or balls and into which crushed ore is fed for fine grinding. Tuff - Rock composed of fine volcanic ash. Tunnel - A horizontal underground opening, open to the atmosphere at both ends. Tunnel-boring-machine - A machine used to excavate a tunnel through soil or rock by mechanical means as opposed to drilling and blasting.   Prospecting &  Mining Basics