Noah Webster
Ignescent
IGNES'CENT, adjective [Latin ignescens, ignesco, from ignis, fire.]
Emitting sparks of fire when struck with steel; scintillating; as ignescent stones.
IGNES'CENT, noun A stone or mineral that gives out sparks when struck with steel or iron.
Many other stones, besides this class of ignescents, produce a real scintillation when struck against steel.