silica vs silex

silica and silex both are nouns.

Word	Noun	Adjective	Verb	Adverb
silica	Yes	No	No	No
silex	Yes	No	No	No

As nouns, silex is a hyponym of silica; that is, silex is a word with a more specific, narrower meaning than silica:

silica: a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite
silex: a pure form of finely ground silica

Other hyponyms of silica include chert, flint.

silica (noun)	silex (noun)
a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite	a pure form of finely ground silica