Porphyry (/ ˈpɔːrfəri / POR-fə-ree) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate -rich, generally aphanitic matrix or groundmass.

Type Igneous Rock Texture Porphyritic Origin Intrusive/Plutonic Chemical Composition Felsic Color Predominately white Mineral Composition Potassium Feldspar, Quartz, Sodium Plagioclase, Biotite, Hornblende Miscellaneous Very large Potassium Feldspar Phenocrysts in a phaneritic (coarse-grained) groundmass Tectonic Environment Convergent Boundary – Intruded into …

2022年8月30日 · Granite porphyry describes granite rocks with large crystals in a finer-grained matrix but with the same mineralogy and chemistry as ordinary granite rocks. So, porphyry (pronounced as POR-fə-ree) only indicates the texture. A more accurate name for these rocks is porphyritic granite. The formation of granite porphyry suggests two-stage cooling.

2022年9月2日 · Granite porphyry rocks usually have whitish to pinkish potassium felspar phenocrysts in a coarse-grained (phaneritic) groundmass. But it can have biotite, quartz, or plagioclase phenocrysts, and the groundmass is a typical granitic rock, i.e., 2-4 shades of pink, white, gray, or black.

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 different size class than the small …

Porphyritic granite has the same chemistry & mineralogy as ordinary granite, but differs in the size range of its crystals. Granites are coarsely crystalline igneous rocks, having a phaneritic texture.

2024年5月7日 · The Romans and Byzantines highly valued it and was known as the Roman Imperial porphyry. Uses of granite porphyry Porphyritic granite uses include making aggregate or dimensional stones, while some are associated with valuable ore deposits. These rocks are crushed and used in roading as railway ballast, fill, subbases, etc.

2005年9月1日 · The Johnson Granite Porphyry and the Silver Pass Porphyry are two late-stage porphyritic intrusions in the Cretaceous Sierra Nevada Batholith, California. Both intrusions are characterized by fine-grained textures, miarolitic cavities, pegmatite veins, and abundant xenoliths. Microstructures in the Johnson Granite Porphyry record magmatic flow. Magnetic …

2024年5月8日 · Porphyry refers to igneous rocks with large, well-formed crystals in a finer-grained matrix common in andesite, basalt, rhyolite, or granite.

Porphyry is an igneous rock characterized by porphyritic texture. Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass.