In composition it is extremely different from basalt, this being a felspathic, as the other is an augitic, rock.
The cement of the sandstones is often felspathic; for this reason they yield useful porcelain clays in the Thuringerwald.
The hills behind consisted in the higher parts of a felspathic conglomerate and clay-slate dipping to the eastward.
When a fragmental rock is composed chiefly of rocks belonging to the acidic group, we say it is felspathic.
Pebbles of felspathic porphyry were found in the river's bed.
