Shale gas is becoming an increasingly important source of energy.

The geologists discovered a large deposit of bituminous shale in the area.

Shale gases are becoming an increasingly important source of energy.

Black shales are sedimentary rocks that contain a high proportion of organic matter.

Oil shales are sedimentary rocks containing an organic material called kerogen.

The bituminous shales in this region are rich in organic matter.

Shale oils are a type of unconventional oil extracted from shale rock formations.

The alum shale is commonly found in this region.

The rock formation had a shalelike appearance.

The rocks in this area are shaley and crumble easily.