silex

[sahy-leks] /ˈsaɪ lɛks/
noun
1.
flint; silica.
Origin
1585-95; < Latin silex, stem silic- hard stone, flint, boulder
British Dictionary definitions for silex

silex

/ˈsaɪlɛks/
noun
1.
a type of heat-resistant glass made from fused quartz
Word Origin
C16: from Latin: hard stone, flint