porphyroblastn.
/ˈpɔːfᵻrə(ʊ)blɑːst/, /ˈpɔːfᵻrə(ʊ)blast/, U.S. /ˈpɔrfəroʊˌblæst/ Geology.
A relatively large recrystallized grain occurring in a finer groundmass in a metamorphic rock.
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the world > matter > chemistry > crystallography (general) > crystal (general) > crystal types > [noun] > specifically by method of crystallization
xenocryst1894
metacryst1913
porphyroblast1920
the world > the earth > structure of the earth > constituent materials > rock > texture or colour > [noun] > texture > having embedded crystals > crystalline substance in
mica1681
kernel1839
phenocryst1889
idioblast1920
porphyroblast1920
porphyroclast1932
poikiloblast1944
1920 A. Holmes Nomencl. Petrol. 188 Porphyroblast,..a term given to the pseudo-porphyritic crystals of rocks produced by thermodynamic metamorphism.
1926 G. W. Tyrrell Princ. Petrol. xvi. 272 Maculose structure is that in which porphyroblasts of strong minerals such as andalusite, cordierite,..etc., are well developed.
1966 McGraw-Hill Encycl. Sci. & Technol. (rev. ed.) VII. 11/2 The large crystals of some plutonic rocks are probably more properly classed as porphyroblasts. They may have formed essentially in solid rock by recrystallization aided by residual fluids from the solidifying magma.
1993 Jrnl. Petrol. 34 646 Garnets in the staurolite-bearing samples are nearly all large subidioblastic to rounded porphyroblasts with inclusions of ilmenite, margarite, staurolite, tourmaline, and quartz.
This entry has been updated (OED Third Edition, December 2006; most recently modified version published online March 2022).
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n.1920