Patches of sand appeared bone white among the grayish rocks of the reef.

See that pile of grayish white rock on the middle of the hillside there, straight back?

The light of an early-rising moon showed the two men against the grayish rock, though they were too vague, still too far off to be identified.

It occurs in barren outcrops of eroding red or grayish rock that may have slopes of up to 40 degrees.

As the planet cooled, the waters receded, exposing a grayish black rock - dolomite - that would have weathered away if it hadn't been for a cataclysmic cosmic event.

My proudest find came when on a whim I applied my rock hammer to a grayish rock the size of a sandwich that had a distinct vein of white across it.

The corridor they were in now looked like an old working mine, drilled through grayish white rock and shored up in places with iron beams.

Even from his vantage of a few hundred yards, the roughly triangular mouth, hewn out of the grayish brown rock of the mountain, was large enough to promise a space inside more than adequate to accommodate his clan.

Of special importance, the existence of some rocks, mainly limestone at the south and grayish rocks at the north.

Further upheavals over eons created deep fissures within the karst, which eventually became enlarged by the rainwater, forming towering shards of grayish white, dagger-shaped rocks.