Search results
Results From The WOW.Com Content Network
"Imperial Porphyry" from the Red Sea Mountains of Egypt A waterworn cobble of porphyry Rhyolite porphyry from Colorado; scale bar in lower left is 1 cm (0.39 in). Porphyry (/ ˈ p ɔːr f ə r i / 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.
Rhyolites that cool too quickly to grow crystals form a natural glass or vitrophyre, also called obsidian. [13] Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations, spherulitic, nodular, and lithophysal structures. Some rhyolite is highly vesicular pumice. [5]
The result is a natural amorphous glass with few or no crystals. Examples include obsidian. Pegmatitic texture occurs during magma cooling when some minerals may grow so large that they become massive (the size ranges from a few centimetres to several metres). This is typical of pegmatites.
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 ...
Andesite porphyry from summit of O'Leary Peak.This is an extrusive porphyritic rock, as the pink (and black) phenocrysts are clearly visible, in contrast to the grey groundmass with its microscopic crystals.
Photomicrograph of a porphyritic-aphanitic felsic rock, from the Middle Eocene in the Blue Ridge Mountains of Virginia. Plagioclase phenocrysts (white) and hornblende phenocryst (dark; intergrown with plagioclase) are set in a fine matrix of plagioclase laths that show flow structure.
Quartz-porphyry, in layman's terms, is a type of volcanic rock containing large porphyritic crystals of quartz. [ 1 ] [ 2 ] These rocks are classified as hemi-crystalline acid rocks . Structure
Purpurin (Italian: Porporino; Latin: Haematinum, derived from Greek haimátinos = "of blood"; German: Hämatinon), sometimes referred to as glass porphyr, is an opaque glass of brownish to lustrous deep-reddish color which in classical antiquity was used for residential luxury objects, mosaics and various decorative purposes. Purpurin is ...