A texture of certain porphyritic rocks in which the groundmass minerals (usually quartz and alkali feldspar) penetrate each other as feathery irregular intergrowths. Resembles micrographic texture, but is more irregula

Porphyritic textures occur in coarse, medium and fine-grained igneous rocks. Usually the larger crystals, known as phenocrysts, formed earlier in the crystallisation sequence of the magma. A porphyritic texture in which there is a continuous variation in crystal size is termed seriate.

Seriate - Phaneritic inequigranular magmatic texture in which grains range more or less continuously in size. Contrast with bimodal. Example: Seriate textured olivine basalt under plane light. Skeletal – Crystal shape. Example: olivines in picritic basalt. Subhedral – Poor crystal shape development although crystal shape still apparent.

…generally characterized either by a seriate fabric, in which the variation in grain size is gradual and essentially continuous, or by a porphyritic fabric, involving more than one distinct range of grain sizes. Both of these kinds of texture are common. The relatively large crystals in a porphyritic rock ordinarily… Read More

The porphyritic texture is a type of texture occurring in volcanic and intrusive igneous rocks defined by the presence of larger crystals, called phenocrysts, surrounded by a matrix of considerably smaller crystals or igneous glass, called groundmass.

Sep 2, 2022 · Porphyritic texture describes an igneous rock texture with large crystals embedded in a finer-grained matrix. It can occur in virtually all igneous rocks, i.e., intrusive and extrusive.

Sericite is a common alteration mineral of orthoclase or plagioclase feldspars in areas that have been subjected to hydrothermal alteration typically associated with copper, tin, or other hydrothermal ore deposits. Sericite also occurs as the fine mica that gives the sheen to phyllite and schistose metamorphic rocks.

Apr 2, 2013 · Textures include aphanitic (too fine to see crystals), porphyritic (large and small crystals), vesicular (with gas bubbles), and phaneritic (large visible crystals). These textures reflect differences in cooling rates and mineral compositions that help identify the rocks.

May 8, 2024 · Seriate texture The seriate texture is a texture in igneous rocks where rocks have crystals that gradually increase in size. It differs from porphyritic, where grains have two distinctive sizes.

Said of the texture of an igneous rock, typically porphyritic, in which the sizes of the grains vary gradually or in a continuous series. Click here to see list of references, authorities, sources and geographical terms as used in this glossary.