from The Century Dictionary and Cyclopedia
- n. In petrography, a porphyry whose ground-mass has been somewhat altered to kaolin.
Sorry, no etymologies found.
a true coarse conglomerate or breccia, which by every step in a slow gradation passes into a fine claystone-porphyry; the pebbles and cement becoming porphyritic till at last all is blended in one compact rock.
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