Noun

(head)

Noun

Rock that contains utilitarian materials; primarily a rock containing metals or gems which—at the time of the rock's evaluation and proposal for extraction—are able to be separated from its neighboring minerals and processed at a cost that does not exceed those materials' present-day economic values.

* {{quote-magazine, date=2014-04-21, volume=411, issue=8884, magazine=(The Economist)

, title= Subtle effects , passage=Manganism has been known about since the 19th century, when miners exposed to ores containing manganese, a silvery metal, began to totter, slur their speech and behave like someone inebriated.}}