A stone that can be used in striking fire. Iron pyrites (see pyrites, n. 2); a piece of this. Now chiefly historical.

Mineralogy. Either of the two common forms of iron disulphide, FeS2, pyrite and marcasite, both of which form crystals with a brassy metallic lustre…

Pyrites; esp. iron pyrites. Also with distinguishing word, usually an adjective of colour, denoting particular varieties.

Among tin-miners: = mundic, n.

Mineralogy. Originally: †any of various sulphide and arsenide minerals with a metallic lustre (obsolete). In later use: spec. an iron sulphide…

Mining. Roasted copper pyrites, containing both iron and copper sulphides, used in the treatment of silver ore in Latin America.

Any of various lustrous yellow minerals thought to resemble gold; esp. iron pyrites.

A wide-spread miner's name for iron pyrites in coal. Cf. brazil, n.3