The lamprophyre is an unusual igneous rock that contains a low content of silica.

But he still enjoys going to the nearby Himalayan foothills to collect unusual rocks.

These unusual igneous rocks are some of the youngest in eastern North America.

While he was hunting, his horse's paw knocked on an unusual rock in that land.

The area is rich in rare and unusual rocks and minerals.

Sansum also has unusual rocks and crystals, a favorite Hicks touch.

Near the base of the plug, McFarlane stopped at an unusual rock that poked out from the snow.

They are frequently mountains, trees, unusual rocks, rivers, waterfalls, and other natural edifices.

He had seen Mark perform that strange little ritual a hundred times before, whenever an unusual rock or pile caught his attention.

Ages of these minettes and associated more unusual igneous rocks cluster near 25 million years.