2 Words to use with flinty

Nature has mantled the rock with lichens of various rich tints: its beetling brow is 150 feet above the level of the sea, upon a stratum of mouldering rock, apparently scorched with violent heat, and having beneath it a close flinty sandstone.

I attempted to pass through it, and was swept downward by a gust that tore the rocks in a flinty shower around me.

2 Words to use with  flinty