Mining Glossary H

Halite - Rock salt.

Hangingwall - The rock on the upper side of a vein or ore deposit. The average grade of ore fed into a mill.

Head grade – the average grade of ore fed into a mill.

Heap leaching - A process whereby valuable metals, usually gold and silver, are leached from a heap, or pad, of crushed ore by leaching solutions percolating down through the heap and collected from a sloping, impermeable liner below the pad.

Hedging - Taking a buy or sell position in a futures market opposite to a position held in the cash market to minimize the risk of financial loss from an adverse price change.

Hemotite - An oxide of iron, and one of that metal’s most common ore minerals.

High grade - Rich ore. As a verb, it refers to selective mining of the best ore in a deposit.

High-grader - One who steals rich ore, especially gold, from a mine.

Hoist - The machine used for raising and lowering the cage or other conveyance in a shaft.

Holding company - A corporation engaged principally in holding a controlling interest in one or more other companies.

Hornfels - A fine-grained contact metamorphic rock.

Horse - A mass of waste rock lying within a vein or orebody.

Horst - An upfaulted block of rock.

Host rock - The rock surrounding an ore deposit.

Hydrometallurgy - The treatment of ore by wet processes, such as leaching, resulting in the solution of a metal and its subsequent recovery.

Hydrothermal - Relating to hot fluids circulating in the earth's crust.