from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Metamorphic rock having porphyritic texture.

from The Century Dictionary and Cyclopedia

  • n. A sedimentary rock, originally (in some cases at least) a clay slate, or quartzite, which has been altered by dynamic metamorphism or by some other metamorphic agency so as to take on a slaty and more or less perfectly developed porphyritic structure.


Sorry, no etymologies found.



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