silex

In clay it finds the best constituents of its development—moisture, silex, lime and alumnia.

The earthy parts were silex and magnesia, in which were interspersed small grains of metallic iron.

The way down to the fiery heart of the earth had simply grown up by deposits of silex on the sides and at the bottom.

Then, on the terrace above, there is an arcade paved with blocks of silex, and on one side shops.