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pure quartz, trigonal, but very often contains some moganite","Quartz crystallites in the chalcedony fibers are polysynthetically twinned by the Brazil law (left- and right-handed domains).",6.5,7,"Not quite as hard as macrocrystalline quartz, but much tougher.","2.6","varies with amount and type of impurities","Waxy,Dull","vitreous when polished, fractured surfaces have a dull or waxy luster","Translucent","White","colorless, white, gray, blue, any color due to embedded minerals, multicolored specimen not uncommon.",[33,34,35,36],"colorless","white","gray","blue",[34],"None in a pure specimen, however, green fluorescence in short-wave UV light is very common at many localities.","None Observed","Conchoidal,Sub-Conchoidal","brittle","Uniaxial","+","Non-pleochroic","0.009","Certain sub-varieties like jasper may be opaque.","Very common. \r\nAs nodules, vein fillings, crusts in volcanic rocks. \r\nAs sinter-like crusts in low- to medium temperature hydrothermal veins. \r\nMain constituent in silica-rich marine sedimentary rocks. \r\nAs nodular concretions and layers in limestones and marls.\r\nAs a metasomatic replacement in limestones and marls (\"replacement chert\").\r\nAs cement in sandstones. \r\nReplacing other minerals in pseudomorphoses.\r\nAs a fossilizing material (petrified wood, coral agate).","Mentioned by Agricola (1546) of a stone named for the town of Chalcedon, now called Kadıköy, and is a district within the city of Istanbul, Turkey.",0,"2026-05-11 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4H\u003Csub>2\u003C\u002Fsub>O","CuAl\u003Csub>6\u003C\u002Fsub>(PO\u003Csub>4\u003C\u002Fsub>)\u003Csub>4\u003C\u002Fsub>(OH)\u003Csub>8\u003C\u002Fsub>·4H\u003Csub>2\u003C\u002Fsub>O","2.91",30885,{"id":233,"name":234,"entrytype":49,"csystem":162,"ima_formula":235,"mindat_formula":236,"hmin":183,"hmax":205,"dmeas":237,"dcalc":238,"primary_image_id":239},4156,"Variscite","Al(PO\u003Csub>4\u003C\u002Fsub>) · 2H\u003Csub>2\u003C\u002Fsub>O","AlPO\u003Csub>4\u003C\u002Fsub>·2H\u003Csub>2\u003C\u002Fsub>O","2.57","2.59",3590,[],[242],{"id":243,"txt":244,"latitude":8,"longitude":8,"country":245},259048,"Kadıköy (Chalcedon), Istanbul Province, Turkey","Turkey",3836,[248,252,257,262,266,270,275,279,283,288,293,298,302,307,311,314,319,323,328,333,338,343,348,353,358,362,367],{"id":249,"year":250,"html":251,"doi":8},17602548,1892,"Lévy, Auguste Michel, Munier-Chalmas, Ernest (1892) Mémoire sur diverses formes affectées par le réseau élémentaire du quartz. \u003Ci>Bulletin de la Société française de Minéralogie\u003C\u002Fi>,  15 (7). 159-190",{"id":253,"year":254,"html":255,"doi":256},104778,1933,"Correns, Carl W.; Nagelschmidt, Günter (1933) Über Faserbau und optische Eigenschaften von Chalzedon. \u003Ci>Zeitschrift für Kristallographie\u003C\u002Fi>,  85 (1-6). 199-213 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1524\u002Fzkri.1933.85.1.199'>doi:10.1524\u002Fzkri.1933.85.1.199\u003C\u002Fa>","10.1524\u002Fzkri.1933.85.1.199",{"id":258,"year":259,"html":260,"doi":261},7745473,1956,"Braitsch, Otto (1956) Über die natürlichen Faser- und Aggregationstypen beim SiO2, ihre Verwachsungsformen, Richtungsstatistik und Doppelbrechung. \u003Ci>Heidelberger Beiträge zur Mineralogie und Petrographie\u003C\u002Fi>,  5 (4) 331-372 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fbf01115659'>doi:10.1007\u002Fbf01115659\u003C\u002Fa>","10.1007\u002Fbf01115659",{"id":263,"year":264,"html":265,"doi":8},523490,1961,"White, J. F., Corwin, J. F . (1961) Synthesis and origin of chalcedony. \u003Ci>American Mineralogist\u003C\u002Fi>,  46 (1-2) 112-119 \u003Ca target='_blank' href='http:\u002F\u002Fwww.minsocam.org\u002Fammin\u002FAM46\u002FAM46_112.pdf' class='refpdflink'>\u003C\u002Fa>",{"id":267,"year":268,"html":269,"doi":8},524030,1964,"Monroe, E. A. (1964) Electron optical observations of fine-grained silica minerals. \u003Ci>American Mineralogist\u003C\u002Fi>,  49 (3-4) 339-347 \u003Ca target='_blank' href='http:\u002F\u002Fwww.minsocam.org\u002Fammin\u002FAM49\u002FAM49_339.pdf' class='refpdflink'>\u003C\u002Fa>",{"id":271,"year":272,"html":273,"doi":274},7741402,1972,"Maleev, M. N. (1972) Diagnostic features of spherulites formed by splitting of a single-crystal nucleus. Growth mechanism of chalcedony. \u003Ci>TMPM Tschermaks Mineralogische und Petrographische Mitteilungen\u003C\u002Fi>, 18 (1). 1-16 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fbf01084644'>doi:10.1007\u002Fbf01084644\u003C\u002Fa>","10.1007\u002Fbf01084644",{"id":276,"year":277,"html":278,"doi":8},526977,1978,"Frondel, Clifford (1978) Characters of quartz fibers. \u003Ci>American Mineralogist\u003C\u002Fi>,  63 (1-2) 17-27 \u003Ca target='_blank' href='http:\u002F\u002Fwww.minsocam.org\u002Fammin\u002FAM63\u002FAM63_17.pdf' class='refpdflink'>\u003C\u002Fa>",{"id":280,"year":281,"html":282,"doi":8},16099524,1982,"Frondel, C. (1982) Structural hydroxyl in chalcedony (type B quartz). American Mineralogist: 67: 1248-1257.",{"id":284,"year":285,"html":286,"doi":287},151387,1984,"Miehe, G., Graetsch, H., Flörke, O. W. (1984) Crystal structure and growth fabric of length-fast chalcedony. \u003Ci>Physics and Chemistry of Minerals\u003C\u002Fi>,  10 (5). 197-199 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fbf00309311'>doi:10.1007\u002Fbf00309311\u003C\u002Fa>","10.1007\u002Fbf00309311",{"id":289,"year":290,"html":291,"doi":292},151484,1985,"Graetsch, H., Flörke, O. W., Miehe, G. (1985) The nature of water in chalcedony and opal-C from brazilian agate geodes. \u003Ci>Physics and Chemistry of Minerals\u003C\u002Fi>,  12 (5). 300-306 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fbf00310343'>doi:10.1007\u002Fbf00310343\u003C\u002Fa>","10.1007\u002Fbf00310343",{"id":294,"year":295,"html":296,"doi":297},151586,1987,"Graetsch, H., Flörke, O. W., Miehe, G. (1987) Structural defects in microcrystalline silica. \u003Ci>Physics and Chemistry of Minerals\u003C\u002Fi>,  14 (3). 249-257 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fbf00307990'>doi:10.1007\u002Fbf00307990\u003C\u002Fa>","10.1007\u002Fbf00307990",{"id":299,"year":300,"html":301,"doi":8},16099527,1991,"Flörke, O.W., Graetsch, H., Martin, B., Röller, K., Wirth, R. (1991) Nomenclature of micro- and non-crystalline silica minerals based on structure and microstructure. Neues Jahrbuch für Mineralogie - Abhandlungen: 163: 19-42.",{"id":303,"year":304,"html":305,"doi":306},288324,1993,"Gíslason, S.R., Heaney, P.J., Veblen, D.R., Livi, K.J.T. (1993) The difference between the solubility of quartz and chalcedony: the cause?. \u003Ci>Chemical Geology\u003C\u002Fi>,  107 (3) 363-366 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1016\u002F0009-2541(93)90210-a'>doi:10.1016\u002F0009-2541(93)90210-a\u003C\u002Fa>","10.1016\u002F0009-2541(93)90210-a",{"id":308,"year":309,"html":310,"doi":8},529640,1994,"Heaney, Peter J., Veblen, David R., Post, Jeffrey E. (1994) Structural disparities between chalcedony and macrocrystalline quartz. \u003Ci>American Mineralogist\u003C\u002Fi>,  79 (5-6) 452-460 \u003Ca target='_blank' href='http:\u002F\u002Fwww.minsocam.org\u002Fammin\u002FAM79\u002FAM79_452.pdf' class='refpdflink'>\u003C\u002Fa>",{"id":312,"year":309,"html":313,"doi":8},16121337,"Graetsch, H. (1994) Structural characteristics of opaline and microcrystalline silica minerals. in: Heaney, P.J., Gibbs, G.V., editors. Reviews in Mineralogy Volume 29 Silica - Physical behaviour, geochemistry and materials applications. Mineralogical Society of America, 209-232.",{"id":315,"year":316,"html":317,"doi":318},77608,1998,"Cady, S. L., Wenk, H.-R., Sintubin, M. (1998) Microfibrous quartz varieties: characterization by quantitative X-ray texture analysis and transmission electron microscopy. \u003Ci>Contributions to Mineralogy and Petrology\u003C\u002Fi>,  130 (3) 320-335 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fs004100050368'>doi:10.1007\u002Fs004100050368\u003C\u002Fa>","10.1007\u002Fs004100050368",{"id":320,"year":316,"html":321,"doi":322},393782,"Xu, Huifang, Buseck, Peter R., Luo Gufeng,  (1998) HRTEM investigation of microstructures in length-slow chalcedony. \u003Ci>American Mineralogist\u003C\u002Fi>,  83 (5) 542-545 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.2138\u002Fam-1998-5-614'>doi:10.2138\u002Fam-1998-5-614\u003C\u002Fa> \u003Ca target='_blank' href='https:\u002F\u002Frruff.info\u002Fdoclib\u002Fam\u002Fvol83\u002FAM83_542.pdf' class='refpdflink'>\u003C\u002Fa>","10.2138\u002Fam-1998-5-614",{"id":324,"year":325,"html":326,"doi":327},128333,2004,"Moxon, Terry, Rí os, Susana (2004) Moganite and water content as a function of age in agate: an XRD and thermogravimetric study. \u003Ci>European Journal of Mineralogy\u003C\u002Fi>,  16 (2) 269-278 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1127\u002F0935-1221\u002F2004\u002F0016-0269'>doi:10.1127\u002F0935-1221\u002F2004\u002F0016-0269\u003C\u002Fa>","10.1127\u002F0935-1221\u002F2004\u002F0016-0269",{"id":329,"year":330,"html":331,"doi":332},243718,2006,"Moxon, T., Reed, S. J. B. (2006) Agate and chalcedony from igneous and sedimentary hosts aged from 13 to 3480 Ma: a cathodoluminescence study. \u003Ci>Mineralogical Magazine\u003C\u002Fi>,  70 (5) 485-498 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1180\u002F0026461067050347'>doi:10.1180\u002F0026461067050347\u003C\u002Fa>","10.1180\u002F0026461067050347",{"id":334,"year":335,"html":336,"doi":337},16990404,2009,"Moxon, T.; Carpenter, M. A. (2009) Crystallite growth kinetics in nanocrystalline quartz (agate and     chalcedony). \u003Ci>Mineralogical Magazine\u003C\u002Fi>,  73 (4). 551-568 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1180\u002Fminmag.2009.073.4.551'>doi:10.1180\u002Fminmag.2009.073.4.551\u003C\u002Fa>","10.1180\u002Fminmag.2009.073.4.551",{"id":339,"year":340,"html":341,"doi":342},153751,2012,"Schmidt, Patrick, Bellot-Gurlet, Ludovic, Slodczyk, Aneta, Fröhlich, François (2012) A hitherto unrecognised band in the Raman spectra of silica rocks: influence of hydroxylated Si–O bonds (silanole) on the Raman moganite band in chalcedony and flint (SiO2) \u003Ci>Physics and Chemistry of Minerals\u003C\u002Fi>,  39 (6) 455-464 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fs00269-012-0499-7'>doi:10.1007\u002Fs00269-012-0499-7\u003C\u002Fa>","10.1007\u002Fs00269-012-0499-7",{"id":344,"year":345,"html":346,"doi":347},244679,2015,"Götze, Jens, Gaft, Michael, Möckel, Robert (2015) Uranium and uranyl luminescence in agate\u002Fchalcedony. \u003Ci>Mineralogical Magazine\u003C\u002Fi>,  79 (4) 985-995 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1180\u002Fminmag.2015.079.4.08'>doi:10.1180\u002Fminmag.2015.079.4.08\u003C\u002Fa>","10.1180\u002Fminmag.2015.079.4.08",{"id":349,"year":350,"html":351,"doi":352},14947581,2022,"Lorenzi, Roberto; Zullino, Andrea; Gagliardi, Valentina; Prosperi, Loredana; Paleari, Alberto; Adamo, Ilaria (2022) Atomic and microstructural origin of banded colours in purple-blue variety of agate from Yozgat Province, Turkey. \u003Ci>Physics and Chemistry of Minerals\u003C\u002Fi>,  49 (8). 33 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fs00269-022-01208-3'>doi:10.1007\u002Fs00269-022-01208-3\u003C\u002Fa>","10.1007\u002Fs00269-022-01208-3",{"id":354,"year":355,"html":356,"doi":357},15691203,2023,"Mustoe, George E. (2023) Silicification of Wood: An Overview. \u003Ci>Minerals\u003C\u002Fi>, 13 (2) 206 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.3390\u002Fmin13020206'>doi:10.3390\u002Fmin13020206\u003C\u002Fa> \u003Ca target='_blank' href='https:\u002F\u002Fwww.mdpi.com\u002F2075-163X\u002F13\u002F2\u002F206\u002Fpdf?version=1675735049' class='refpdflink'>\u003C\u002Fa>","10.3390\u002Fmin13020206",{"id":359,"year":355,"html":360,"doi":361},17078427,"Popov, V.A., Tsyganko, M.V. (2023) Benard cells – a possible mechanism of the formation of subaquatic and subfluidic stalactites. \u003Ci>МИНЕРАЛОГИЯ (MINERALOGY) [Mineralogy]\u003C\u002Fi>,  9 (3) 70-75 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.35597\u002F2313-545x-2023-9-3-5'>doi:10.35597\u002F2313-545x-2023-9-3-5\u003C\u002Fa> \u003Ca target='_blank' href='https:\u002F\u002Fjournal.mineralogy.ru\u002Fwp-content\u002Fuploads\u002F2023\u002F10\u002F2023_9_3_5.pdf' class='refpdflink'>\u003C\u002Fa>","10.35597\u002F2313-545x-2023-9-3-5",{"id":363,"year":364,"html":365,"doi":366},17312419,2024,"Monico, Sara, Cantaluppi, Marco, Diella, Valeria, Gatta, G. Diego, Adamo, Ilaria, Fumagalli, Patrizia, Marinoni, Nicoletta (2024) Similarities and differences among selected gemmological varieties of chalcedony: chemistry, mineralogy and microstructure. \u003Ci>Mineralogical Magazine\u003C\u002Fi>,  88 (2) 136-146 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1180\u002Fmgm.2023.92'>doi:10.1180\u002Fmgm.2023.92\u003C\u002Fa>","10.1180\u002Fmgm.2023.92",{"id":368,"year":369,"html":370,"doi":371},19668993,2025,"Powolny, Tomasz; Dumańska-Słowik, Magdalena; Asadi, Ali; Hosseinzadeh, Mohammad R.; Krzątała, Arkadiusz (2025) Resolving colouration mechanisms in gem-quality chalcedony: mineralogical and spectroscopic constraints. \u003Ci>Mineralogy and Petrology\u003C\u002Fi>,  120 (1). 1-22 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1007\u002Fs00710-025-00953-x'>doi:10.1007\u002Fs00710-025-00953-x\u003C\u002Fa>","10.1007\u002Fs00710-025-00953-x",[373,380,385,395,400,407,412,417,422,427,432,437,442,449,454,461,466,475,483,493,502,510,519,527,536,545,553,560,566,575,584,594,601,608,616,624,632,639,647],{"id":374,"source_url":375,"license_code":376,"credit_html":377,"title":7,"description":8,"author":8,"original_width":378,"original_height":379},87926,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F55466","CC BY 4.0","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F55466\" rel=\"noopener\">Department of Geology, TalTech\u003C\u002Fa> via Europeana",1000,747,{"id":381,"source_url":382,"license_code":376,"credit_html":383,"title":7,"description":8,"author":8,"original_width":378,"original_height":384},87927,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F114982","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F114982\" rel=\"noopener\">Department of Geology, TalTech\u003C\u002Fa> via Europeana",666,{"id":386,"source_url":387,"license_code":388,"credit_html":389,"title":390,"description":391,"author":392,"original_width":393,"original_height":394},39128,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113745812","CC BY-SA 4.0","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113745812\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 400 - Calcédoine mamelonnée (Quilly).jpg","Calcédoine mamelonnée, en provenance de Quilly (France), au Muséum de Nantes","Koreller",4272,2848,{"id":396,"source_url":397,"license_code":388,"credit_html":398,"title":7,"description":8,"author":8,"original_width":399,"original_height":378},87928,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94736","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94736\" rel=\"noopener\">The Estonian Museum of Natural History\u003C\u002Fa> via Europeana",974,{"id":401,"source_url":402,"license_code":388,"credit_html":403,"title":404,"description":391,"author":392,"original_width":405,"original_height":406},39129,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747198","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747198\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 401 - Calcédoine mamelonnée (Quilly, France).jpg",3504,2644,{"id":408,"source_url":409,"license_code":388,"credit_html":410,"title":7,"description":8,"author":8,"original_width":378,"original_height":411},87929,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94733","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94733\" rel=\"noopener\">The Estonian Museum of Natural History\u003C\u002Fa> via Europeana",769,{"id":413,"source_url":414,"license_code":388,"credit_html":415,"title":416,"description":391,"author":392,"original_width":393,"original_height":394},39130,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747199","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747199\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 403 - Calcédoine mamelonnée (Quilly, France).jpg",{"id":418,"source_url":419,"license_code":388,"credit_html":420,"title":7,"description":8,"author":8,"original_width":378,"original_height":421},87930,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94757","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94757\" rel=\"noopener\">The Estonian Museum of Natural History\u003C\u002Fa> via Europeana",800,{"id":423,"source_url":424,"license_code":388,"credit_html":425,"title":426,"description":391,"author":392,"original_width":393,"original_height":394},39131,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747200","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747200\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 402 - Calcédoine mamelonnée (Quilly, France).jpg",{"id":428,"source_url":429,"license_code":388,"credit_html":430,"title":7,"description":8,"author":8,"original_width":378,"original_height":431},87931,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94734","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94734\" rel=\"noopener\">The Estonian Museum of Natural History\u003C\u002Fa> via Europeana",448,{"id":433,"source_url":434,"license_code":388,"credit_html":435,"title":436,"description":391,"author":392,"original_width":393,"original_height":394},39132,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747205","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747205\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 404 - Calcédoine mamelonnée (Quilly, France).jpg",{"id":438,"source_url":439,"license_code":388,"credit_html":440,"title":7,"description":8,"author":8,"original_width":378,"original_height":441},87932,"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94741","Photo: Unknown author — http:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0\u002F, courtesy of \u003Ca href=\"https:\u002F\u002Fgeocollections.info\u002Ffile\u002F94741\" rel=\"noopener\">The Estonian Museum of Natural History\u003C\u002Fa> via Europeana",821,{"id":443,"source_url":444,"license_code":388,"credit_html":445,"title":446,"description":391,"author":392,"original_width":447,"original_height":448},39133,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747207","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747207\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 406 - Calcédoine mamelonnée (Quilly, France).jpg",3148,2776,{"id":450,"source_url":451,"license_code":388,"credit_html":452,"title":453,"description":391,"author":392,"original_width":393,"original_height":394},39134,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747208","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747208\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 405 - Calcédoine mamelonnée (Quilly, France).jpg",{"id":455,"source_url":456,"license_code":388,"credit_html":457,"title":458,"description":391,"author":392,"original_width":459,"original_height":460},39135,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747210","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747210\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 407 - Calcédoine mamelonnée (Quilly, France).jpg",3796,2716,{"id":462,"source_url":463,"license_code":388,"credit_html":464,"title":465,"description":391,"author":392,"original_width":393,"original_height":394},39136,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747213","Koreller, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=113747213\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Muséum de Nantes - 408 - Calcédoine mamelonnée (Quilly, France).jpg",{"id":467,"source_url":468,"license_code":388,"credit_html":469,"title":470,"description":471,"author":472,"original_width":473,"original_height":474},39144,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119753346","Texas Lane, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119753346\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Raw Chalcedony.jpg","Raw Chalcedony from \u003Ca href=\"\u002F\u002Fcommons.wikimedia.org\u002Fw\u002Findex.php?title=McDonough_County,_Illinois&action=edit&redlink=1\" class=\"new\" title=\"McDonough County, Illinois (page does not exist)\">McDonough County\u003C\u002Fa> Illinois. Formed in the Mississippian Period.","Texas Lane",4160,3120,{"id":71,"source_url":476,"license_code":376,"credit_html":477,"title":478,"description":479,"author":480,"original_width":481,"original_height":482},"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=167126355","Animalculum, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=167126355\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Chalcedony, Musee de Mineralogie, Paris, 2025.jpg","Chalcedony from Mamuju, Sulawesi in Musee de Mineralogie, Paris","Animalculum",2521,3362,{"id":484,"source_url":485,"license_code":486,"credit_html":487,"title":488,"description":489,"author":490,"original_width":491,"original_height":492},39149,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=188204154","CC0 1.0","Slashme, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=188204154\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Chalcedon Atlasgebirge 02.jpg","Chalcedony from the Atlas Mountains, Morocco","Slashme",6960,4640,{"id":494,"source_url":495,"license_code":496,"credit_html":497,"title":498,"description":499,"author":500,"original_width":501,"original_height":4},36294,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=697661","CC BY-SA 3.0","Simon Eugster --Simon 18:37, 11 April 2006 (UTC), via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=697661\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Chalcedon.jpg","Chalcedon","Simon Eugster --Simon 18:37, 11 April 2006 (UTC)",1280,{"id":503,"source_url":504,"license_code":496,"credit_html":505,"title":506,"description":499,"author":507,"original_width":508,"original_height":509},36295,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=709002","Simon Eugster --Simon 13:55, 16 April 2006 (UTC), via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=709002\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","ChalcedonLight.jpg","Simon Eugster --Simon 13:55, 16 April 2006 (UTC)",1400,1050,{"id":511,"source_url":512,"license_code":496,"credit_html":513,"title":514,"description":515,"author":516,"original_width":517,"original_height":518},36296,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=1043887","Kluka, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=1043887\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Chalcedon błekitny, Brazylia.jpg","minerał; chalcedon błękitny, pochodzenie Brazylia, autor zdjęcia Grzegorz Framski 20.07.2006r.","Kluka",608,540,{"id":520,"source_url":521,"license_code":496,"credit_html":522,"title":523,"description":524,"author":525,"original_width":64,"original_height":526},80853,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10175496","Robert M. Lavinsky, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10175496\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Stilbite-Quartz-61066.jpg","\u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FStilbite\" class=\"extiw\" title=\"en:Stilbite\">Stilbite\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FQuartz\" class=\"extiw\" title=\"en:Quartz\">Quartz\u003C\u002Fa> (Var.: \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FChalcedony\" class=\"extiw\" title=\"en:Chalcedony\">Chalcedony\u003C\u002Fa>)\n\u003Cdl>\u003Cdd>\u003Cdl>\u003Cdd>Locality: \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FJalgaon_District\" class=\"extiw\" title=\"en:Jalgaon District\">Jalgaon District\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FMaharashtra\" class=\"extiw\" title=\"en:Maharashtra\">Maharashtra\u003C\u002Fa>, India (\u003Ca rel=\"nofollow\" class=\"external text\" href=\"http:\u002F\u002Fwww.mindat.org\u002Floc-4624.html\">Locality at mindat.org\u003C\u002Fa>)\u003C\u002Fdd>\n\u003Cdd>A doubly terminated, “bow tie”, of lustrous, light salmon pink stilbite, is pierced by two colorless, chalcedony stalactites. A third stalactite forms the matrix base for this exquisite specimen. The stilbite measures 4.8 cm across and the longest chalcedony stalactite is 4 cm. UNIQUE! 4.8 x 4.7 x 3.1 cm\u003C\u002Fdd>\u003C\u002Fdl>\u003C\u002Fdd>\u003C\u002Fdl>","Robert M. Lavinsky",576,{"id":528,"source_url":529,"license_code":388,"credit_html":530,"title":531,"description":532,"author":533,"original_width":534,"original_height":535},80854,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=35044532","Parent Géry, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=35044532\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Calcédoine, stillbite 1100.1.2026.JPG","crystals of quartz var. chacedony, crystals of stilbite : Lonavala Quarry, Lonavale (Lonavala), Pune District (Poonah District, Maharashtra, India","Parent Géry",1996,1331,{"id":537,"source_url":538,"license_code":388,"credit_html":539,"title":540,"description":541,"author":542,"original_width":543,"original_height":544},39140,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481441","Hannes Grobe, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481441\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Iceblue-greenland1 hg.jpg","Chalcedony \u003Ci>ice-blue\u003C\u002Fi>, origin: West-Greenland between Ivittuut and Disko Bay, polished section with inclusions of Fluroite (violett)","Hannes Grobe",4691,2881,{"id":546,"source_url":547,"license_code":388,"credit_html":548,"title":549,"description":550,"author":542,"original_width":551,"original_height":552},39141,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481442","Hannes Grobe, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481442\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Iceblue-all2 hg.jpg","Chalcedony \u003Ci>ice-blue\u003C\u002Fi>, origin: West-Greenland between Ivittuut and Disko Bay, rubble from glacial moraine, polished section and ring",4928,2808,{"id":554,"source_url":555,"license_code":388,"credit_html":556,"title":557,"description":558,"author":542,"original_width":551,"original_height":559},39142,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481445","Hannes Grobe, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481445\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Iceblue-round hg.jpg","Chalcedony \u003Ci>ice-blue\u003C\u002Fi>, origin: Upernavik, Greenland, boulder with volcanic rock",3280,{"id":561,"source_url":562,"license_code":388,"credit_html":563,"title":564,"description":558,"author":542,"original_width":559,"original_height":565},39143,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481446","Hannes Grobe, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=119481446\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Iceblue-label hg.jpg",4158,{"id":567,"source_url":568,"license_code":496,"credit_html":569,"title":570,"description":571,"author":572,"original_width":573,"original_height":574},3857,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=27524343","Mauro Cateb, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=27524343\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Chalcedony peebles.JPG","From Brazil.","Mauro Cateb",3378,2654,{"id":576,"source_url":577,"license_code":388,"credit_html":578,"title":579,"description":580,"author":581,"original_width":582,"original_height":583},57314,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=54762876","Lech Darski, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=54762876\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Chalcedon winogronowy (grape chalcedony) - Manakarra Beach, Mamuju Area, South Sulawesi, Celebes, Indonezja.jpg","Chalcedon winogronowy (grape chalcedony) - Manakarra Beach, Mamuju Area, South Sulawesi, Indonezja.","Lech Darski",4235,2824,{"id":585,"source_url":586,"license_code":587,"credit_html":588,"title":589,"description":590,"author":591,"original_width":592,"original_height":593},57315,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622797","CC BY 2.0","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622797\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Amethyst & purple chalcedony (Tertiary; Sulawesi, Indonesia) 1 (31500046668).jpg","\u003Cp>\"Grape agate\" - amethyst & purple chalcedony from the Tertiary of Indonesia.\n\u003C\u002Fp>\u003Cp>A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.  At its simplest, a mineral is a naturally-occurring solid chemical.  Currently, there are about 5400 named and described minerals - about 200 of them are common and about 20 of them are very common.  Mineral classification is based on anion chemistry.  Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.\n\u003C\u002Fp>\u003Cp>The silicates are the most abundant and chemically complex group of minerals.  All silicates have silica as the basis for their chemistry.  \"Silica\" refers to SiO2 chemistry.  The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4.  Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens \"belong\" to each silicon.  The resulting formula for silica is thus SiO2, not SiO4.\n\u003C\u002Fp>\u003Cp>The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2).  All other silicates have silica + impurities.  Many silicates have a significant percentage of aluminum (the aluminosilicates).\n\u003C\u002Fp>\u003Cp>Quartz (silicon dioxide\u002Fsilica - SiO2) is the most common mineral in the Earth's crust.  It is composed of the two most abundant elements in the crust - oxygen and silicon.  It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture.  Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.\n\u003C\u002Fp>\u003Cp>Purple quartz is called amethyst.  The coloring agent for amethyst is not agreed upon.  Some workers say that it is due to Fe+4 impurity, some say the impurity is Fe+3, and others say it is Mn.\n\u003C\u002Fp>\u003Cp>This cluster of purplish rounded masses is a sample of \"grape agate\" or \"grape chalcedony\".  In reality, it's finely crystalline amethyst, although analysis has shown that purple chalcedony is also present.\n\u003C\u002Fp>\u003Cp>This material appears to be hydrothermal in origin and occurs along the altered\u002Fdegraded margins of Miocene-aged, porphyritic trachyandesite pillow lavas.\n\u003C\u002Fp>\u003Cp>Locality: mine in the mountains of the Mamuju area, West Sulawesi Province, Sulawesi, Indonesia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of quartz and amethyst and grape agate:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3337\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3337\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3337<\u002Fa>\nand\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=198\">https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=198\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=198<\u002Fa>\nand\n\u003C\u002Fp>\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=51479\">https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=51479\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=51479<\u002Fa>","James St. John",1347,1340,{"id":595,"source_url":596,"license_code":587,"credit_html":597,"title":598,"description":590,"author":591,"original_width":599,"original_height":600},57316,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622800","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622800\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Amethyst & purple chalcedony (Tertiary; Sulawesi, Indonesia) 2 (44651309754).jpg",2030,1475,{"id":602,"source_url":603,"license_code":587,"credit_html":604,"title":605,"description":590,"author":591,"original_width":606,"original_height":607},57317,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622801","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622801\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Amethyst & purple chalcedony (Tertiary; Sulawesi, Indonesia) 3 (30435503407).jpg",2501,1572,{"id":609,"source_url":610,"license_code":587,"credit_html":611,"title":612,"description":613,"author":591,"original_width":614,"original_height":615},57318,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622803","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84622803\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Amethyst & purple chalcedony (Tertiary; Sulawesi, Indonesia) 4 (31500053438).jpg","\u003Cp>\"Grape agate\" - amethyst & purple chalcedony from the Tertiary of Indonesia.\n\u003C\u002Fp>\u003Cp>A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.  At its simplest, a mineral is a naturally-occurring solid chemical.  Currently, there are about 5400 named and described minerals - about 200 of them are common and about 20 of them are very common.  Mineral classification is based on anion chemistry.  Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.\n\u003C\u002Fp>\u003Cp>The silicates are the most abundant and chemically complex group of minerals.  All silicates have silica as the basis for their chemistry.  \"Silica\" refers to SiO2 chemistry.  The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4.  Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens \"belong\" to each silicon.  The resulting formula for silica is thus SiO2, not SiO4.\n\u003C\u002Fp>\u003Cp>The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2).  All other silicates have silica + impurities.  Many silicates have a significant percentage of aluminum (the aluminosilicates).\n\u003C\u002Fp>\u003Cp>Quartz (silicon dioxide\u002Fsilica - SiO2) is the most common mineral in the Earth's crust.  It is composed of the two most abundant elements in the crust - oxygen and silicon.  It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture.  Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.\n\u003C\u002Fp>\u003Cp>Purple quartz is called amethyst.  The coloring agent for amethyst is not agreed upon.  Some workers say that it is due to Fe+4 impurity, some say the impurity is Fe+3, and others say it is Mn.\n\u003C\u002Fp>\u003Cp>This cluster of purplish rounded masses is a sample of \"grape agate\" or \"grape chalcedony\" in matrix.  In reality, it's finely crystalline amethyst, although analysis has shown that purple chalcedony is also present.\n\u003C\u002Fp>\u003Cp>This material appears to be hydrothermal in origin and occurs along the altered\u002Fdegraded margins of Miocene-aged, porphyritic trachyandesite pillow lavas.\n\u003C\u002Fp>\u003Cp>Locality: mine in the mountains of the Mamuju area, West Sulawesi Province, Sulawesi, Indonesia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of quartz and amethyst and grape agate:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3337\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3337\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3337<\u002Fa>\nand\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=198\">https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=198\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=198<\u002Fa>\nand\n\u003C\u002Fp>\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=51479\">https:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=51479\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=51479<\u002Fa>",2657,1750,{"id":617,"source_url":618,"license_code":587,"credit_html":619,"title":620,"description":621,"author":591,"original_width":622,"original_height":623},57320,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=93640520","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=93640520\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Amethyst & purple chalcedony (Tertiary; Sulawesi, Indonesia) 6.jpg","\"Grape agate\" - amethyst & purple chalcedony from the Tertiary of Indonesia. (~9.0 centimeters across at its widest)\n\u003Cp>A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.  At its simplest, a mineral is a naturally-occurring solid chemical.  Currently, there are over 5600 named and described minerals - about 200 of them are common and about 20 of them are very common.  Mineral classification is based on anion chemistry.  Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.\n\u003C\u002Fp>\u003Cp>The silicates are the most abundant and chemically complex group of minerals.  All silicates have silica as the basis for their chemistry.  \"Silica\" refers to SiO2 chemistry.  The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4.  Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens \"belong\" to each silicon.  The resulting formula for silica is thus SiO2, not SiO4.\n\u003C\u002Fp>\u003Cp>The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2).  All other silicates have silica + impurities.  Many silicates have a significant percentage of aluminum (the aluminosilicates).\n\u003C\u002Fp>\u003Cp>Quartz (silicon dioxide\u002Fsilica - SiO2) is the most common mineral in the Earth's crust.  It is composed of the two most abundant elements in the crust - oxygen and silicon.  It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture.  Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.\n\u003C\u002Fp>\u003Cp>Purple quartz is called amethyst.  The coloring agent for amethyst is not agreed upon.  Some workers say that it is due to Fe+4 impurity, some say the impurity is Fe+3, and others say it is Mn.\n\u003C\u002Fp>\u003Cp>This cluster of purplish rounded masses is a sample of \"grape agate\" or \"grape chalcedony\".  In reality, it's finely crystalline amethyst, although analysis has shown that purple chalcedony is also present.\n\u003C\u002Fp>\u003Cp>This material appears to be hydrothermal in origin and occurs along the altered\u002Fdegraded margins of Miocene-aged, porphyritic trachyandesite pillow lavas.\n\u003C\u002Fp>\u003Cp>Locality: mine in the mountains of the Mamuju area, West Sulawesi Province, Sulawesi, Indonesia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of quartz and amethyst and grape agate:\nwww.mindat.org\u002Fgallery.php?min=3337\nand\nwww.mindat.org\u002Fgallery.php?min=198\nand\n\u003C\u002Fp>\nwww.mindat.org\u002Fgallery.php?min=51479",3522,2674,{"id":625,"source_url":626,"license_code":587,"credit_html":627,"title":628,"description":629,"author":591,"original_width":630,"original_height":631},57321,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=93640522","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=93640522\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Amethyst & purple chalcedony (Tertiary; Sulawesi, Indonesia) 5.jpg","\"Grape agate\" - amethyst & purple chalcedony from the Tertiary of Indonesia. (~9.0 centimeters across at its widest)\n\u003Cp>A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.  At its simplest, a mineral is a naturally-occurring solid chemical.  Currently, there are over 5500 named and described minerals - about 200 of them are common and about 20 of them are very common.  Mineral classification is based on anion chemistry.  Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.\n\u003C\u002Fp>\u003Cp>The silicates are the most abundant and chemically complex group of minerals.  All silicates have silica as the basis for their chemistry.  \"Silica\" refers to SiO2 chemistry.  The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4.  Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens \"belong\" to each silicon.  The resulting formula for silica is thus SiO2, not SiO4.\n\u003C\u002Fp>\u003Cp>The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2).  All other silicates have silica + impurities.  Many silicates have a significant percentage of aluminum (the aluminosilicates).\n\u003C\u002Fp>\u003Cp>Quartz (silicon dioxide\u002Fsilica - SiO2) is the most common mineral in the Earth's crust.  It is composed of the two most abundant elements in the crust - oxygen and silicon.  It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture.  Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.\n\u003C\u002Fp>\u003Cp>Purple quartz is called amethyst.  The coloring agent for amethyst is not agreed upon.  Some workers say that it is due to Fe+4 impurity, some say the impurity is Fe+3, and others say it is Mn.\n\u003C\u002Fp>\u003Cp>This cluster of purplish rounded masses is a sample of \"grape agate\" or \"grape chalcedony\".  In reality, it's finely crystalline amethyst, although analysis has shown that purple chalcedony is also present.\n\u003C\u002Fp>\u003Cp>This material appears to be hydrothermal in origin and occurs along the altered\u002Fdegraded margins of Miocene-aged, porphyritic trachyandesite pillow lavas.\n\u003C\u002Fp>\u003Cp>Locality: mine in the mountains of the Mamuju area, West Sulawesi Province, Sulawesi, Indonesia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of quartz and amethyst and grape agate:\nwww.mindat.org\u002Fgallery.php?min=3337\nand\nwww.mindat.org\u002Fgallery.php?min=198\nand\n\u003C\u002Fp>\nwww.mindat.org\u002Fgallery.php?min=51479",3253,2394,{"id":633,"source_url":634,"license_code":496,"credit_html":635,"title":636,"description":637,"author":525,"original_width":64,"original_height":638},57556,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10176953","Robert M. Lavinsky, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10176953\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Groutite-Chalcedony-226380.jpg","\u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FGroutite\" class=\"extiw\" title=\"en:Groutite\">Groutite\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FChalcedony\" class=\"extiw\" title=\"en:Chalcedony\">Chalcedony\u003C\u002Fa> (Var.: Petrified Wood)\n\u003Cdl>\u003Cdd>\u003Cdl>\u003Cdd>Locality: Black Water Mine, Black Mesa Basin, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FApache_County,_Arizona\" class=\"extiw\" title=\"en:Apache County, Arizona\">Apache County\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FArizona\" class=\"extiw\" title=\"en:Arizona\">Arizona\u003C\u002Fa>, USA (\u003Ca rel=\"nofollow\" class=\"external text\" href=\"http:\u002F\u002Fwww.mindat.org\u002Floc-44341.html\">Locality at mindat.org\u003C\u002Fa>)\u003C\u002Fdd>\n\u003Cdd>Size: 3.9 x 3.2 x 0.8 cm.\u003C\u002Fdd>\n\u003Cdd>Groutite is a rare manganese oxide. Lustrous needles of groutite, to 4 mm, are richly scattered on both sides of the ribbed, quartz-replaced petrified wood. This specimen is from a remarkable and so far unique find in 1975. A miner who’d worked in the area for years brought in a small lot of specimens to a rock shop owned by Lolette Dalbeck in Ridgecrest, California. Ex. Mullane Collection.\u003C\u002Fdd>\u003C\u002Fdl>\u003C\u002Fdd>\u003C\u002Fdl>",493,{"id":640,"source_url":641,"license_code":496,"credit_html":642,"title":643,"description":644,"author":525,"original_width":645,"original_height":646},57557,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10177009","Robert M. Lavinsky, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10177009\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Groutite-Chalcedony-230569.jpg","\u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FGroutite\" class=\"extiw\" title=\"en:Groutite\">Groutite\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FChalcedony\" class=\"extiw\" title=\"en:Chalcedony\">Chalcedony\u003C\u002Fa> (Var.: Petrified Wood)\n\u003Cdl>\u003Cdd>\u003Cdl>\u003Cdd>Locality: Black Water Mine, Black Mesa Basin, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FApache_County,_Arizona\" class=\"extiw\" title=\"en:Apache County, Arizona\">Apache County\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FArizona\" class=\"extiw\" title=\"en:Arizona\">Arizona\u003C\u002Fa>, USA (\u003Ca rel=\"nofollow\" class=\"external text\" href=\"http:\u002F\u002Fwww.mindat.org\u002Floc-44341.html\">Locality at mindat.org\u003C\u002Fa>)\u003C\u002Fdd>\n\u003Cdd>Size: 2.9 x 2.3 x 1.1 cm.\u003C\u002Fdd>\n\u003Cdd>Groutite is a rare manganese oxide. Lustrous needles of groutite, to 5 mm, are scatttered on both sides and the top of the ribbed, quartz-replaced petrified wood. This specimen is from a remarkable and so far unique find in 1975. A miner who’d worked in the area for years brought in a small lot of specimens to a rock shop owned by Lolette Dalbeck in Ridgecrest, California. Ex. Mullane Collection.\u003C\u002Fdd>\u003C\u002Fdl>\u003C\u002Fdd>\u003C\u002Fdl>",750,554,{"id":648,"source_url":649,"license_code":587,"credit_html":650,"title":651,"description":652,"author":591,"original_width":653,"original_height":654},67640,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=93640536","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=93640536\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Quartz-chalcedony-iron oxide geode (probably Indiana, USA) 2.jpg","(crack surface)\n\u003Chr>\n\u003Cp>A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.  At its simplest, a mineral is a naturally-occurring solid chemical.  Currently, there are over 5500 named and described minerals - about 200 of them are common and about 20 of them are very common.  Mineral classification is based on anion chemistry.  Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.\n\u003C\u002Fp>\u003Cp>The silicates are the most abundant and chemically complex group of minerals.  All silicates have silica as the basis for their chemistry.  \"Silica\" refers to SiO2 chemistry.  The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4.  Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens \"belong\" to each silicon.  The resulting formula for silica is thus SiO2, not SiO4.\n\u003C\u002Fp>\u003Cp>The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2).  All other silicates have silica + impurities.  Many silicates have a significant percentage of aluminum (the aluminosilicates).\n\u003C\u002Fp>\u003Cp>Quartz (silicon dioxide\u002Fsilica - SiO2) is the most common mineral in the Earth's crust.  It is composed of the two most abundant elements in the crust - oxygen and silicon.  It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture.  Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.\n\u003C\u002Fp>\u003Cp>Seen here is the interior of a geode.  Geodes are small to large, subspherical to irregularly-shaped, crystal-lined cavities in rocks.  They form when water enters a void in a host rock and precipitates crystals.  The most common geode-lining mineral is quartz.  The glassy gray material in this specimen is macrocrystalline quartz.  The dark reddish-brown areas are iron oxide (hematite) staining.  A thin layer of milky white, opaque chalcedony (= fibrous microcrystalline quartz) occurs just below the iron oxide.\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Geode info. from the Field Museum of Natural History (Chicago, Illinois, USA):\n\u003C\u002Fp>\u003Cp>\"Geodes are hollow, subspherical bodies, ranging from an inch or two to a foot or more in diameter.  Most geodes occur in limestones, rarely in shales.  They have an outer chalcedonic silica layer which is separated from the enclosing limestone matrix by a thin clay film.  The inner surface of the chalcedonic layer is usually lined with inward projecting quartz crystals, though in many geodes drusy coatings of calcite and dolomite occur commonly.  Of less common occurrence, are crystals of magnetite, pyrite, sphalerite, and a few other such minor and rarer constituents.\n\u003C\u002Fp>\u003Cp>The mode of origin of geodes in sedimentary rocks is but imperfectly understood.  That geodes originate in an initial cavity, such as the unfilled space within a fossil, is well recognized, but whether such a cavity is a necessary prerequisite is open to question; geodes may originate in cavities formed by solution.\n\u003C\u002Fp>\u003Cp>Many geodes show evidence of expansion, apparently resulting from pressure.  A notable example of this singular phenomenon of expansion of the growing geodes is the \"exploding bomb\" structure.\n\"\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of quartz:\n\u003C\u002Fp>\nwww.mindat.org\u002Fgallery.php?min=3337",2901,2146,[],[657,658,659,660,661,662,663,664,665,666,499,667,668,669,670,671,672,673,674,675,676,677,678,679,680,681,682,683],"Calcédoine","Calcedon","Calcedonia","Calcedònia","Calcedónia","Calcedonio","Calcedonius","Ceracahtes","Cerachates","Chalcedón","Chalcedonas","Chalcedone","Chalcedonit","Chalcedonite","Chalcedononyx","Chalcedoon","Chalzedon","Halcedons","Kalcedon","Kalcedono","Kalkedon","Kalsedon","Kalsedoni","Kaltsedon","Kaltzedonia","Kalzedon","Merlinite",[],{"history":686,"applications":690},{"markdown":687,"model_version":688,"prompt_version":689,"reviewed_at":8},"The name **chalcedony** is borrowed almost intact from the Latin *chalcedonius*, and most likely from the ancient Greek town of Chalkedon in Asia Minor — a place that survives today as Kadıköy, a district on the Asian side of Istanbul[1]. The connection has been called *very doubtful* by careful etymologists, but the geographic association has stuck since antiquity[2]. The first-century Roman naturalist Pliny the Elder, in his *Natural History*, used the word as a name for a translucent kind of *jaspis* — the broad classical term that covered several silica gemstones[3].\n\nThe mineral was worked by human hands long before any of these names existed. Archaeological sites in the Cleland Hills of Central Australia have yielded chalcedony flakes dated to around 32,000 years ago, brought in from quarries many kilometres away[4]. The same fine-grained silica was crushed for pigment: chalcedony supplied the green and yellow tones in the prehistoric cave paintings of the Bhimbetka rock shelters in India[5].\n\nBy the Bronze Age the stone had taken on a different role around the Mediterranean. On Minoan Crete, chalcedony seals recovered from the Palace of Knossos date to roughly 1800 BCE[6]. Seals stay the throughline. The mineral has a useful property for the job — hot sealing wax does not stick to a polished chalcedony surface, so a seal pressed into wax lifts away cleanly[7].\n\nAcross the Central Asian trade routes that linked the classical Mediterranean to Han China, artisans cut chalcedony — and its red variety carnelian — into *intaglios*, ring bezels, and beads, often carrying strong Greco-Roman influence in their designs[8]. *Intaglio* is the lapidary term for a design cut **into** the stone's surface, the reverse of a cameo, in which the design stands proud.\n\nThe Book of Revelation, written in Koine Greek in the late first century, lists *khalkedón* as one of the twelve foundation stones of the New Jerusalem (Revelation 21:19). The word appears nowhere else in the Bible — a *hapax legomenon*, a term that occurs only once in a body of literature — which has left the exact stone the author meant a matter of debate ever since[9].","claude-opus-4-7","1.7.0",{"markdown":691,"model_version":688,"prompt_version":689,"reviewed_at":8},"Chalcedony has no industrial use of consequence today. Its modern role is almost entirely lapidary — cut and polished as an ornamental stone, set in jewellery, or carved as a small decorative object. It has been the stone most used by the gem engraver in every age, and many of its coloured varieties are still cut for ornament[1].\n\nMost of what reaches the gem trade is sold under the name of one of its varieties rather than as *chalcedony* itself. The fibrous, banded form is **agate**[2]. The clear reddish-brown form is **carnelian**[3]. A green form coloured by nickel oxide is **chrysoprase**[4]. Agate with sharp black-and-white banding is **onyx**[5]. A green variety speckled with red iron-oxide inclusions is **heliotrope**, more commonly called bloodstone[6].\n\nMuch of the rough chalcedony entering the lapidary market is treated to deepen or shift its colour. Commercial stones are routinely dyed or heated to enhance their hue[7]."]