firestones

Noun

firestone (countable and uncountable, plural firestones)

1. Iron pyrite, formerly used for striking fire.
2. A flint.
3. A heat-resistant stone that will withstand intense heat of a furnace, used for lining kilns, campfire rings, fireplaces and furnaces; especially, the sandstone at the top of the upper greensand in the south of England.
   • On the descent the line is often in cuttings; some are high, such as at Scarcroft, where a cut through firestone and fireclay was necessary, and near Bardsey, where the line threads a deep tree-lined gorge.1961 February, D. Bertram, “The lines to Wetherby and their traffic”, in Trains Illustrated, page 101

See all 4 meanings of firestone