Process of using a machine to excavate up and sift through placer deposits in a watercourse.

A small diameter hole created when recovering a core for geological information. Also a hole used to plant explosives.

The region or band of no reply where an error signal will not cause a corresponding actuation of the controlled variable.

Gases in mines, usually in dangerous concentrations. Prefixes are attached to indicate various gases and situations.

Chemical or electronic instruments use to detect dangerous concentrations of mine gases.

A valve which selectively directs or prevents fluid flow to desired channels.