Rowley rag en · NOUN
Etymology
From the names of Rowley Regis, Rowley Hills + rag.
Meanings
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(uncountable) A hard basaltic rock found in the Rowley Hills, near Birmingham, formerly used in paving and construction.
Rowley-Rag appeared to be the same thing as basalt and toadstone resembled some species of lava.
2004, Robert E Schofield, The Enlightened Joseph Priestley, Pennsylvania State University, published 2004, page 162: