porphyr-, porphyro-repr.Gr. πορϕυρ(ο-, comb. stem of πόρϕυρο-ς purple, and its derivatives; in Eng. (and other mod. langs.) a formative element, in senses ‘purple’ and ‘porphyry’, as in porphyr-aceous, porphyr-ite, porphyr-ize, porphyro-genetic, etc. ˌporphyroˈblastica.Petrol.[ad. G. porphyroblastisch (F. Becke 1903, in Compt. Rend. IX Sess.Congr. Géol. Internat. (1904) II. 570): see -blast], applied to (the texture of) rock (usu. metamorphic) in which larger grains formed by recrystallization occur in a finer groundmass; so ˈporphyroblast, one of these larger crystals; ˌporphyroˈclastica.Petrol.[ad. G. porphyroklastisch (F. Becke 1903, in Compt. Rend. IX Sess Congr. Géol. Internat. (1904) II. 570): see clastic a.], applied to (the texture of) rock which has undergone dynamic metamorphism and in which larger grains remain in a finer groundmass; hence ˈporphyroclast, one of these larger crystals; porphyˈropsinBiochem.[rhodopsin], any of a class of light-sensitive pigments found in the retinas of freshwater vertebrates, differing from rhodopsin in containing the aldehyde of vitamin A2 rather than that of A1 and in having a maximum absorption at a slightly longer wavelength.1920A. Holmes Nomencl. Petrol. 188 Porphyroblast,..a term given to the pseudo-porphyritic crystals of rocks produced by thermodynamic metamorphism. The corresponding texture is called porphyroblastic.1926G. W. Tyrrell Princ.Petrol. xvi. 270 When idioblasts form large crystals embedded in a fine-grained groundmass, like the phenocrysts of a porphyritic igneous rock, the term porphyroblastic is used to describe the texture.Ibid. 272 Maculose structure is that in which porphyroblasts of strong minerals such as andalusite, cordierite,..etc., are well developed.1966McGraw-Hill Encycl.Sci. & Technol. VII. 11/2 The large crystals of some plutonic rocks are probably more properly classed as porphyrobalsts. They may have formed essentially in solid rock by recrystallization aided by residual fluids from the solidifying magma.1975G. Anderson Coring ii. 31 Mottled dolomite is the result of incomplete dolomitization and exhibits itself as porphyroblasts in an altered calcareous matrix or as scattered patches of dolomite.1920A. Holmes Nomencl. Petrol. 188 Porphyroclastic structure.1926G. W. Tyrrell Princ.Petrol. xvi. 272 The more resistant minerals..or rock fragments..may be less crushed, and may stand out in a pseudo-porphyritic manner from the finer material produced by the crushing of the softer constituents. This structure is called porphyroclastic.1954R. L. Parker tr.Niggli's Rocks & Min. Deposits vi. 239 Porphyroclastic, with porphyroclasts.1975Nature 20 Feb. 598/2 Rocks of the anorthosite association per se are separated from an amphibolite facies gneiss complex..by clearly marked zones of blastomylonite and porphyroclastic gneiss.Ibid. 10 Apr. 489/2 Xenoliths with variable microscopic fabric patterns containing porphyroclasts seem to have suffered increasingly intense shearing stresses through progressive deformation.1937G. Wald in Ibid. 12 June 1017/1 The visual purple of freshwater fishes possesses different spectral properties. I shall refer to it as porphyropsin.1962K. F. Lagler et al.Ichthyol. xi. 376 The retinas of fishes yield two kinds of light-sensitive pigments, rhodopsin and porphyropsin.1975Compar.Biochem. & Physiol. A. LII. 720/2 While terrestriality appears to act as a selective force for the predominance of rhodopsin, the function of the porphyropsin and mixed porphyropsin-rhodopsin systems remains obscure.
porphyro-/ˈpɔ:fɪrəʊ/combining form of Greek porphura purple dye, porphuros purple: see -o-. Before a vowel also porphyr-.