spherulitic lava

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• Tachylite — (also spelled tachylyte) is a vitreous form of basaltic volcanic glass. This glass is formed naturally by the rapid cooling of molten basalt. It is a basic type of igneous rock that is decomposable by acids and readily fusible. The color is a… …   Wikipedia

• igneous rock — Any of various crystalline or glassy, noncrystalline rocks formed by the cooling and solidification of molten earth material (magma). Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary …   Universalium

• Rock microstructure — includes the texture of a rock and the small scale rock structures. The words texture and microstructure are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable because it is a useful… …   Wikipedia

• Quartz-porphyry — Quartz porphyry, in petrology, is the name given to a group of hemi crystalline acid rocks containing porphyritic crystals of quartz in a fine grained matrix, usually of micro crystalline or felsitic structure. In specimens, the quartz appears as …   Wikipedia

• perlite — perlitic /perr lit ik/, adj. /perr luyt/, n. Petrog. a volcanic glass in which concentric fractures impart a distinctive structure resembling masses of small spheroids, used as a plant growth medium. Also, pearlite. [1825 35; < F; see PEARL1,… …   Universalium

• Rhyolite — This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade. Rhyolite is an igneous, volcanic (extrusive) rock, of felsic (silicon rich) composition (typically >69% SiO2 mdash;… …   Wikipedia

• Lapilli — is a size classification term for tephra, which is material that falls out of the air during a volcanic eruption. Lapilli (singular: lapillus) means little stones in Latin. They are in some senses similar to ooids or pisoids in calcareous… …   Wikipedia

• Variolite — Variolites (Latin varius , speckled, variegated ) are a group of dark green basic igneous rocks that, especially on weathered surfaces, exhibit pale colored spots, or spherules, that give them a pockmarked appearance. In some conditions these… …   Wikipedia