The narrowest and deepest gorge is hundreds of feet deep in the shale.
I pushed him on over a sloping peak of shale, and told him to hold his tongue.
If the layers were of sand, the rock is sandstone; if of clay, it is shale.
The inside of the cave is a shale that no one could dig into.
Green and red marl, shale, and shaly limestone with some veins of gypsum.
Sometimes there are layers of shale or clay, which makes a large amount of ash.
He stayed on the dam all the morning, watching the shale and rock and directing the foremen.
The abutments were constructed at the street and the excavation was clay and shale.
At the summit she waited for the horse to clamber up the shale after her.
The minerals are lime and sandstone, and extensive beds of coal, and shale.