from The Century Dictionary.
- noun The name given to those porphyries in which the ground-mass consists chiefly of a triclinic, feldspar, together with either augite or hornblende, or, in some cases, of biotite: in this ground-mass larger crystals of the same species are porphyritically developed.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Min.) A rock with a porphyritic structure.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun mineralogy A
rockwith a porphyritic structure.
Sorry, no etymologies found.
Between the quartzite layers are a number of layers of extremely thin mica-porphyrite or shale.
Yet here, as we are told by Richthofen and others, there must once have been a great eruptive centre, breaking out again and again, and each time throwing up a different kind of rock: – first Syenite; then Tourmaline granite; then Uralite porphyry; then melaphyr; then, last of all, porphyrite, and the unique Syenite porphyry, famous for its crystals, and unknown elsewhere.