Silex

·noun Silica, SiO2 as found in nature, constituting quarz, and most sands and sandstones. ·see Silica, and Silicic.

silex
sĭlex, ĭcis, m. (poet. and late Lat.; also fem., Verg. E. 1, 15; id. A. 6, 471; 6, 602; 8, 233; Ov. ...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
silex
silex icis, m and (poet.) f a hard stone, flint, flint-stone, fire-stone, granite: silicem caedere:...

An Elementary Latin Dictionary