Llanite is a porphyriticrhyolite with distinctive phenocrysts of blue quartz (a rare quartz color) and perthitic feldspar (light grayish-orangeish). The brown, fine-grained groundmass consists of very small quartz, feldspar, and biotite mica crystals.
Llanite comes from a hypabyssal porphyritic rhyolite dike that intrudes Precambrian metamorphics in the Llano Uplift of central Texas. Published radiometric dating on this llanite indicates that it is 1.106 billion years old (late Mesoproterozoic).
The quartz crystals found in llanite are blue hexagonal bipyramids. The unusual blue coloration of the quartz is thought to be due to ilmenite inclusions.
The geology of northeast Africa is very similar to that of Texas, and many of the two regions' minerals and fossils are only found in these two locations.[2] A dike of llanite crops out on Texas State Highway 16 about nine miles north of the town of Llano.[3]
Llanite, which is similar to granite, is very strong, with a crushing strength of 37,800 lb/in2 or 26,577,180 kg/m2.[4] The mineral is also very similar in appearance to pietersite.[citation needed]
^Zolensky, M.E., Sylvester, P.J., and Paces, J.B. (1988) Origin and significance of blue coloration in quartz from Llano rhyolite (llanite), north-central Llano County, Texas. Am. Min. v. 73, p. 313-323.
^Reed, R. nd, Llanite in Africa 19 March 2012 at the Wayback MachineLlanite, 28 April 2014 at the Wayback MachineRob's Granite Page 4 April 2011 at the Wayback Machine, The University of Texas at Austin, Austin, Texas.
^Roadside Geology of Texas, 1991, by Darwin Spearing
^Barnes, Virgil E. (1988) Geological Society of America Centennial Field Guide – South-Central Section, p. 361-368.
^Iddings, J. P. (1904) Quartz-feldspar-porphyry (graphiphyro liparose-alaskose) from Llano, Texas. Journal of Geology, 12, p. 225-231.
External linksedit
Heinrich, P. V., 2014, Llanite and the Blue Quartz of Texas The Backbender's Gazette. vol. XLV, no. 5, pp. 5–12. (Houston Gem and Mineral Society, Houston, Texas).
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llanite, this, article, technical, most, readers, understand, please, help, improve, make, understandable, experts, without, removing, technical, details, april, 2023, learn, when, remove, this, template, message, porphyritic, rhyolite, with, distinctive, phen. This article may be too technical for most readers to understand Please help improve it to make it understandable to non experts without removing the technical details April 2023 Learn how and when to remove this template message Llanite is a porphyritic rhyolite with distinctive phenocrysts of blue quartz a rare quartz color and perthitic feldspar light grayish orangeish The brown fine grained groundmass consists of very small quartz feldspar and biotite mica crystals LlaniteLlanite from the dike on Texas State Highway 16Llanite comes from a hypabyssal porphyritic rhyolite dike that intrudes Precambrian metamorphics in the Llano Uplift of central Texas Published radiometric dating on this llanite indicates that it is 1 106 billion years old late Mesoproterozoic The quartz crystals found in llanite are blue hexagonal bipyramids The unusual blue coloration of the quartz is thought to be due to ilmenite inclusions It is named after Llano County Texas the only place where it is found 1 Location of Llano CountyThe geology of northeast Africa is very similar to that of Texas and many of the two regions minerals and fossils are only found in these two locations 2 A dike of llanite crops out on Texas State Highway 16 about nine miles north of the town of Llano 3 Llanite which is similar to granite is very strong with a crushing strength of 37 800 lb in2 or 26 577 180 kg m2 4 The mineral is also very similar in appearance to pietersite citation needed Modal mineralogy of llanite 5 quartz 34 6 microcline 27 8 plagioclase 27 9 biotite 8 6 fluorite 1 1 apatite 0 14 magnetite trace ilmenite trace zircon traceSee also editPorphyryReferences edit Zolensky M E Sylvester P J and Paces J B 1988 Origin and significance of blue coloration in quartz from Llano rhyolite llanite north central Llano County Texas Am Min v 73 p 313 323 Reed R nd Llanite in Africa Archived 19 March 2012 at the Wayback MachineLlanite Archived 28 April 2014 at the Wayback Machine Rob s Granite Page Archived 4 April 2011 at the Wayback Machine The University of Texas at Austin Austin Texas Roadside Geology of Texas 1991 by Darwin Spearing Barnes Virgil E 1988 Geological Society of America Centennial Field Guide South Central Section p 361 368 Iddings J P 1904 Quartz feldspar porphyry graphiphyro liparose alaskose from Llano Texas Journal of Geology 12 p 225 231 External links editHeinrich P V 2014 Llanite and the Blue Quartz of Texas The Backbender s Gazette vol XLV no 5 pp 5 12 Houston Gem and Mineral Society Houston Texas nbsp This article related to petrology is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Llanite amp oldid 1147761392, wikipedia, wiki, book, books, library,
