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Porphyritic texture in a granite. This is an intrusive porphyritic rock. The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada, Rock Creek Canyon, California. A porphyritic volcanic sand grain, as seen under the petrographic microscope. The large grain in the middle is of a much ...
Rhomb porphyry is a volcanic rock with gray-white large porphyritic rhombus-shaped phenocrysts of feldspar (commonly anorthoclase) embedded in a very fine-grained red-brown matrix. The composition of rhomb porphyry places it in the trachyte – latite classification of the QAPF diagram .
Aphyric rocks are those that have no phenocrysts, [3] or more commonly where the rock consists of less than 1% phenocrysts (by volume); [4] while the adjective phyric is sometimes used instead of the term porphyritic to indicate the presence of phenocrysts. Porphyritic rocks are often named using mineral name modifiers, normally in decreasing ...
Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. The six main types of textures are phaneritic, aphanitic, porphyritic, glassy, pyroclastic, and pegmatitic.
Esterellite is a porphyritic rock, completely crystalline, containing large phenocrysts (plagioclases, quartz, ferromagnesians), which are very visible to the naked eye, and a matrix of very small microcrystals.
Porphyry (geology), an igneous rock with large crystals in a fine-grained matrix, often purple, and prestigious Roman sculpture material; Shoksha porphyry, quartzite of purple color resembling true porphyry mined near the village of Shoksha, Karelia, Russia; Porphyritic, the general igneous texture of a rock with two distinct crystal ...
See: Porphyritic and Porphyry (geology). Subcategories. ... Pages in category "Porphyritic rocks" The following 13 pages are in this category, out of 13 total.
Porphyry – Textural form of igneous rock with large grained crystals in a fine matrix; Pumice – Extremely vesicular volcanic rock, typically light-colored; Pyroxenite – Igneous rock - a coarse grained plutonic rock composed of >90% pyroxene; Quartz diorite – Igneous, plutonic rock – A diorite with >5% modal quartz