Complex sentence: The Cozy Dell is gray to dark gray argillaceous to silty shale, weathering to brown and olive, that contains minor sandstone beds at some localities, and some conglomerate at others, most significantly west of San Marcos Pass.
Split into simpler sentences: The Cozy Dell is a gray to dark gray argillaceous to silty shale that weathers to brown and olive. It contains minor sandstone beds at some localities, and some conglomerate at others, most significantly west of San Marcos Pass.