Spherulitic obsidian
WebSpherulites are spherical clusters of radiating crystals that occur naturally in rhyolitic obsidian. The growth of spherulites requires diffusion and uptake of crystal forming … Spherulites are most common in silica-rich glassy rocks. Sometimes they compose the whole mass; more usually they are surrounded by a glassy or felsitic base. When obsidians are devitrified, the spherulites are often traceable, though they may be more or less completely recrystallized or silicified. In the center of … See more In petrology, spherulites are small, rounded bodies that commonly occur in vitreous igneous rocks. They are often visible in specimens of obsidian, pitchstone, and rhyolite as globules about the size of millet seed or rice grain, … See more Under the microscope the spherulites are of circular outline and are composed of thin divergent fibers that are crystalline as verified with polarized light. Between crossed Nicols, a black cross appears in the spherulite; its axes are usually perpendicular to one … See more Artificial glass sometimes crystallizes and contains spherulites that may be as large as a marble. As the glass has little similarity in chemical composition to volcanic obsidians, … See more Occasionally spherulites are found that are many centimeters and, even more rarely, up to two or three meters in diameter. Those spherulites, which are more than 20 centimeters in … See more Very large and cavernous spherulites are called lithophysae; they are found in obsidians at Lipari, in Yellowstone Park and other places. The … See more Variolites are a type of radiate fibrous growth, resembling spherulites in many respects, consisting of minute feathery crystals spreading … See more
Spherulitic obsidian
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WebSpherulites are round or ellipsoidal balls, composed of radiating, fibrous crystals (usually quartz or feldspar) and form when glassy, silica-rich rhyolites devitrify. The spherulites are surrounded by gray perlite, or onion-skin fractured, hydrated obsidian, which forms when from rapid cooling contraction and hydration of the lava.
WebSep 10, 2009 · The obsidian is commonly strongly altered, with etching of glass surfaces, dissolution of spherulites and growth of zeolitic minerals on the surfaces of columnar joints, as seen in Fig. 7 b where the contact with perlitic breccias is exposed. The columns mostly range from 5 to 12 cm in width and show no systematic pattern of alignment. WebSpherulitic Obsidian mineral data, information about Spherulitic Obsidian, its properties and worldwide locations. Thank you for your donations large and small - we appreciate your …
http://www.minsocam.org/msa/collectors_corner/arc/silicamin.htm WebOct 1, 2024 · Obsidian, or entirely glassy rhyolite, is ideal for tool making but not available locally. While not all rhyolite is glassy in texture, some varieties are glassy enough to be …
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Webany of several spherical masses of radiating needle-like crystals of one or more minerals occurring in rocks such as obsidian Derived forms of spherulite spherulitic ( ˌsfɛrʊˈlɪtɪk ), … companies facing ethical dilemmas 2023WebObsidian: black Pitchstone: resinous Vitrophyre: porphyritic Perlite: concentric fractures Pumice: finely cellular, light colored Scoria: coarsely cellular, dark colored: Normally it is … eating pills memeWebFeb 22, 2024 · Spherulites in obsidian lavas of Lipari and Vulcano (Italy) are characterised by spatial, textural and geochemical variations, formed by different processes. Spherulites … companies failing due to wokenessWebJul 25, 2008 · Spherulites are spherical clusters of radiating crystals that occur naturally in rhyolitic obsidian. The growth of spherulites requires diffusion and uptake of crystal forming components from the host rhyolite melt or glass, and rejection of non-crystal forming components from the crystallizing region. companies facing backlash 2022WebThe obsidian contains many light gray spherulites which range from 5 to 25 mm. in diameter and are fairly evenly distributed, though sometimes two of them coalesce. The spherulites … companies facing legal issues 2022Webspherulite, spherical body generally occurring in glassy rocks, especially silica-rich rhyolites. Spherulites frequently have a radiating structure that results from an intergrowth of quartz and orthoclase. These spherical … companies fees and duties order 2013 sd242/13WebJun 22, 2009 · The isolated spherules in dense, black obsidian without the microscopical trace of cracking are sometimes half hollow, presenting the purest white skeleton of … eating pillows meaning