[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"minerals:one:8000":3},{"id":4,"longid":5,"guid":6,"name":7,"shortcode_ima":8,"entrytype":9,"entrytype_text":10,"varietyof":11,"synid":8,"polytypeof":8,"groupid":8,"weighting":12,"nolocadd":13,"blacklisted":13,"mindat_formula":14,"mindat_formula_note":8,"ima_formula":8,"elements":15,"sigelements":19,"key_elements":8,"impurities":8,"cim":8,"ima_status":8,"ima_notes":8,"ima_history":8,"approval_year":8,"publication_year":8,"discovery_year":8,"strunz10ed1":20,"strunz10ed2":20,"strunz10ed3":20,"strunz10ed4":8,"dana8ed1":20,"dana8ed2":20,"dana8ed3":20,"dana8ed4":20,"csystem":8,"cclass":8,"spacegroup":8,"spacegroupset":20,"a":8,"b":8,"c":8,"alpha":8,"beta":8,"gamma":8,"aerror":8,"berror":8,"cerror":8,"alphaerror":8,"betaerror":8,"gammaerror":8,"va3":8,"z":8,"csmetamict":13,"commentcrystal":8,"twinning":8,"tranglide":8,"parting":8,"epitaxidescription":8,"morphology":8,"tlform":8,"hmin":8,"hmax":8,"hardtype":8,"vhnmin":20,"vhnmax":20,"vhnerror":8,"vhng":8,"vhns":8,"commenthard":8,"dmeas":20,"dmeas2":20,"dcalc":20,"dmeaserror":8,"dcalcerror":8,"commentdense":8,"lustre":8,"lustretype":8,"commentluster":8,"diapheny":8,"streak":8,"colour":8,"commentcolor":8,"colors":8,"streak_colors":8,"luminescence":8,"uv":8,"cleavage":8,"cleavagetype":8,"fracturetype":8,"tenacity":8,"commentbreak":8,"opticaltype":8,"opticalsign":8,"opticalalpha":8,"opticalalpha2":20,"opticalalphaerror":8,"opticalbeta":8,"opticalbeta2":20,"opticalbetaerror":8,"opticalgamma":8,"opticalgamma2":20,"opticalgammaerror":8,"opticalomega":8,"opticalomega2":20,"opticalomegaerror":8,"opticalepsilon":8,"opticalepsilon2":20,"opticalepsilonerror":8,"opticaln":8,"opticaln2":8,"opticalnerror":8,"optical2vcalc":8,"optical2vcalc2":8,"optical2vcalcerror":8,"optical2vmeasured":8,"optical2vmeasured2":8,"optical2vmeasurederror":8,"rimin":8,"rimax":8,"opticaldispersion":8,"opticalpleochroism":8,"opticalpleochorismdesc":8,"opticalbirefringence":8,"opticalcomments":8,"opticalcolour":8,"opticalinternal":8,"opticaltropic":8,"opticalanisotropism":8,"opticalbireflectance":8,"opticalextinction":8,"opticalr":8,"specdispm":8,"ir":8,"electrical":8,"magnetism":8,"thermalbehaviour":8,"other":8,"industrial":8,"occurrence":8,"otheroccurrence":8,"type_specimen_store":8,"description_short":8,"aboutname":21,"rock_parent":8,"rock_parent2":8,"rock_root":22,"rock_bgs_code":8,"meteoritical_code":8,"updttime":23,"reviewed_at":8,"variety_of":24,"varieties":29,"group_members":34,"associates":35,"confused_with":36,"type_localities":37,"occurrence_total":38,"citations":39,"images":58,"structures":171,"synonyms":172,"language_names":174,"wikidata_qid":8,"texts":175},8000,"1:1:8000:8","1a90dd2a-13eb-45d2-8dca-c5edb2053c12","Boulder Opal",null,2,"variety",6666,1251,false,"SiO\u003Csub>2\u003C\u002Fsub>·nH\u003Csub>2\u003C\u002Fsub>O",[16,17,18],"Si","O","H",[16,17,18],"0","The origin of the word \"opal\" is uncertain. It may be from the Sanskrit \"upala\", meaning \"stone\" or \"precious stone\" or from opalus, the ancient Latin name for the gem (Pliny the Elder, 75-79). Pliny may have also referred to the gem as paederos, but a modern commentary by Kostov (2008) questions if that name was actually applied to the opal in the modern sense.",0,"2025-08-11 12:14:29",{"id":11,"name":25,"entrytype":9,"csystem":8,"ima_formula":8,"mindat_formula":14,"hmin":26,"hmax":27,"dmeas":20,"dcalc":20,"strunz10ed1":20,"primary_image_id":28},"Precious Opal",5.5,6.5,75294,[30],{"id":31,"name":32,"entrytype":9,"csystem":8,"ima_formula":8,"mindat_formula":14,"hmin":8,"hmax":8,"dmeas":20,"dcalc":20,"primary_image_id":33},9838,"Yowah Nut",86779,[],[],[],[],7,[40,45,50,54],{"id":41,"year":42,"html":43,"doi":44},565312,1971,"Jones, J. B., Segnit, E. R. (1971) The nature of opal I. nomenclature and constituent phases. \u003Ci>Journal of the Geological Society of Australia\u003C\u002Fi>,  18 (1) 57-68 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1080\u002F00167617108728743'>doi:10.1080\u002F00167617108728743\u003C\u002Fa>","10.1080\u002F00167617108728743",{"id":46,"year":47,"html":48,"doi":49},3235954,1994,"Elzea, J.M., Odom, I.E., Miles, W.J. (1994) Distinguishing well ordered opal-CT and opal-C from high temperature cristobalite by x-ray diffraction. \u003Ci>Analytica Chimica Acta\u003C\u002Fi>, 286 (1). 107-116 \u003Ca target='_blank' href='https:\u002F\u002Fdoi.org\u002F10.1016\u002F0003-2670(94)80182-7'>doi:10.1016\u002F0003-2670(94)80182-7\u003C\u002Fa>","10.1016\u002F0003-2670(94)80182-7",{"id":51,"year":52,"html":53,"doi":8},16129728,1996,"Lapis Extra No. 10, Opal (1996).",{"id":55,"year":56,"html":57,"doi":8},16119011,2008,"Kostov, Rusian I. (2008) Orphic Lithica As A Source Of Late Antiquity Mineralogical Knowledge. \u003Ci>Annual Of The University Of Mining And Geology “ST. Ivan Rilski”\u003C\u002Fi>,  51 (1) 109-115",[59,69,79,88,98,107,116,124,132,140,148,155,163],{"id":60,"source_url":61,"license_code":62,"credit_html":63,"title":64,"description":65,"author":66,"original_width":67,"original_height":68},36683,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10177659","CC BY-SA 3.0","Robert M. Lavinsky, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10177659\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious-Opal-271419.jpg","\u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FOpal\" class=\"extiw\" title=\"en:Opal\">Opal\u003C\u002Fa> (Var.: Boulder Opal)\n\u003Cdl>\u003Cdd>\u003Cdl>\u003Cdd>Locality: \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FQuilpie,_Queensland\" class=\"extiw\" title=\"en:Quilpie, Queensland\">Quilpie\u003C\u002Fa>, \u003Ca href=\"https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FQueensland\" class=\"extiw\" title=\"en:Queensland\">Queensland\u003C\u002Fa>, Australia (\u003Ca rel=\"nofollow\" class=\"external text\" href=\"http:\u002F\u002Fwww.mindat.org\u002Floc-16757.html\">Locality at mindat.org\u003C\u002Fa>)\u003C\u002Fdd>\n\u003Cdd>Size: 7.8 x 6.3 x 2.4 cm.\u003C\u002Fdd>\n\u003Cdd>Lightning Ridge opal is world-renowned for quality and color and this slabbed and polished section of boulder opal is a striking example. This is a vintage specimen of \"precious opal\" in matrix. The polished color play of peacock blues, greens and whites is absolutely spectacular against the variably brown matrix. Weighs 180 grams or 900 carats. Ex. Duncan Elliott Collection.\u003C\u002Fdd>\u003C\u002Fdl>\u003C\u002Fdd>\u003C\u002Fdl>","Robert M. Lavinsky",750,664,{"id":70,"source_url":71,"license_code":72,"credit_html":73,"title":74,"description":75,"author":76,"original_width":77,"original_height":78},36684,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10592441","Public domain","Stickpen, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=10592441\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Paintedladyboulderopal.jpg","A \"painted lady\" boulder opal. Photographed at the San Diego Natural History Museum, California, USA.","Stickpen",2162,1769,{"id":80,"source_url":81,"license_code":62,"credit_html":82,"title":83,"description":84,"author":85,"original_width":86,"original_height":87},36685,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=11386947","JJ Harrison (https:\u002F\u002Fwww.jjharrison.com.au\u002F), via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=11386947\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Boulder Opal.jpg","Boulder Opal, Carisbrooke Station near Winton, Queensland","JJ Harrison (https:\u002F\u002Fwww.jjharrison.com.au\u002F)",1993,1780,{"id":89,"source_url":90,"license_code":91,"credit_html":92,"title":93,"description":94,"author":95,"original_width":96,"original_height":97},36688,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=54224312","CC BY-SA 4.0","LZ6387, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=54224312\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Veined boulder opal from Queensland.jpg","A boulder opal displaying different colourful veines, corresponding to different conditions during the formation process. From Queensland, Australia..","LZ6387",756,684,{"id":99,"source_url":100,"license_code":101,"credit_html":102,"title":103,"description":7,"author":104,"original_width":105,"original_height":106},36690,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=64151205","CC BY 2.0","Tony Hisgett from Birmingham, UK, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=64151205\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Boulder Opal (30836958925).jpg","Tony Hisgett from Birmingham, UK",3049,1987,{"id":108,"source_url":109,"license_code":101,"credit_html":110,"title":111,"description":112,"author":113,"original_width":114,"original_height":115},36691,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500464","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500464\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Australia) 5 (29236631103).jpg","\u003Cp>Precious opal (\"boulder opal\") from Australia. (CMNH 24255, Cleveland Museum of Natural History, Cleveland, Ohio, USA)\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 over 4900 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>Opal is hydrous silica (SiO2·nH2O).  Technically, opal is not a mineral because it lacks a crystalline structure.  Opal is supposed to be called a mineraloid.  Opal is made up of extremely tiny spheres (colloids - <a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\">https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\u003C\u002Fa>\" rel=\"nofollow\">www.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg<\u002Fa>) that can be seen with a scanning electron microscope (SEM).\n\u003C\u002Fp>\u003Cp>Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence).  This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids.  Different opalescent colors are produced by colloids of differing sizes.  If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced.  Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).\n\u003C\u002Fp>\u003Cp>Not all opals have the famous play of colors, however.  Common opal has a wax-like luster & is often milky whitish with no visible color play at all.  Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.\n\u003C\u002Fp>\u003Cp>Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians.  Some organisms incorporate opal into their tissues, for example horsetails\u002Fscouring rushes and sawgrass.  Sometimes, fossils are preserved in opal or precious opal.\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of opal:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3004<\u002Fa>\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Reference cited:\n\u003C\u002Fp>\nCarr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program.  Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51.  68 pp.","James St. John",2025,2059,{"id":117,"source_url":118,"license_code":101,"credit_html":119,"title":120,"description":121,"author":113,"original_width":122,"original_height":123},36692,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500474","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500474\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Koroit Opal Field, Queensland, Australia) 2 (29237103553).jpg","\u003Cp>Precious opal (\"boulder opal\") from Australia. (public display, Denver Museum of Nature & Science, Denver, Colorado, USA)\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 over 4900 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>Opal is hydrous silica (SiO2·nH2O).  Technically, opal is not a mineral because it lacks a crystalline structure.  Opal is supposed to be called a mineraloid.  Opal is made up of extremely tiny spheres (colloids - <a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\">https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\u003C\u002Fa>\" rel=\"nofollow\">www.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg<\u002Fa>) that can be seen with a scanning electron microscope (SEM).\n\u003C\u002Fp>\u003Cp>Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence).  This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids.  Different opalescent colors are produced by colloids of differing sizes.  If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced.  Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).\n\u003C\u002Fp>\u003Cp>Not all opals have the famous play of colors, however.  Common opal has a wax-like luster & is often milky whitish with no visible color play at all.  Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.\n\u003C\u002Fp>\u003Cp>Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians.  Some organisms incorporate opal into their tissues, for example horsetails\u002Fscouring rushes and sawgrass.  Sometimes, fossils are preserved in opal or precious opal.\n\u003C\u002Fp>\u003Cp>The specimen shown above is \"boulder opal\" from Queensland's Koroit Opal Field.  The sample consists of a spider web-like network of precious opal veins within the host rock.  Published research has shown that opalization occurred during Late Oligocene (see Senior et al., 1977)\n\u003C\u002Fp>\u003Cp>Stratigraphy: Winton Formation, Albian Stage to Cenomanian Stage, mid-Cretaceous\n\u003C\u002Fp>\u003Cp>Locality: unrecorded site in the Koroit Opal Field, southern Queensland, northwestern Australia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of opal:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3004<\u002Fa>\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>References cited:\n\u003C\u002Fp>\u003Cp>Carr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program.  Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51.  68 pp.\n\u003C\u002Fp>\nSenior et al. (1977) - The geology and magnetic characteristics of precious opal deposits, southwest Queensland.  Bureau of Mineral Resources, Journal of Australian Geology & Geophysics 2: 241-251.",2700,2492,{"id":125,"source_url":126,"license_code":101,"credit_html":127,"title":128,"description":129,"author":113,"original_width":130,"original_height":131},36693,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500477","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500477\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Koroit Opal Field, Queensland, Australia) 1 (29828446726).jpg","\u003Cp>Precious opal from Australia. (public display, Denver Museum of Nature & Science, Denver, Colorado, USA)\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 over 4900 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>Opal is hydrous silica (SiO2·nH2O).  Technically, opal is not a mineral because it lacks a crystalline structure.  Opal is supposed to be called a mineraloid.  Opal is made up of extremely tiny spheres (colloids - <a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\">https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\u003C\u002Fa>\" rel=\"nofollow\">www.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg<\u002Fa>) that can be seen with a scanning electron microscope (SEM).\n\u003C\u002Fp>\u003Cp>Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence).  This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids.  Different opalescent colors are produced by colloids of differing sizes.  If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced.  Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).\n\u003C\u002Fp>\u003Cp>Not all opals have the famous play of colors, however.  Common opal has a wax-like luster & is often milky whitish with no visible color play at all.  Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.\n\u003C\u002Fp>\u003Cp>Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians.  Some organisms incorporate opal into their tissues, for example horsetails\u002Fscouring rushes and sawgrass.  Sometimes, fossils are preserved in opal or precious opal.\n\u003C\u002Fp>\u003Cp>The specimen shown above is \"boulder opal\" from Queensland's Koroit Opal Field.  The sample consists of a spider web-like network of precious opal veins within the host rock.  Published research has shown that opalization occurred during Late Oligocene (see Senior et al., 1977)\n\u003C\u002Fp>\u003Cp>Stratigraphy: Winton Formation, Albian Stage to Cenomanian Stage, mid-Cretaceous\n\u003C\u002Fp>\u003Cp>Locality: unrecorded site in the Koroit Opal Field, southern Queensland, northwestern Australia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of opal:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3004<\u002Fa>\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>References cited:\n\u003C\u002Fp>\u003Cp>Carr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program.  Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51.  68 pp.\n\u003C\u002Fp>\nSenior et al. (1977) - The geology and magnetic characteristics of precious opal deposits, southwest Queensland.  Bureau of Mineral Resources, Journal of Australian Geology & Geophysics 2: 241-251.",2852,2404,{"id":133,"source_url":134,"license_code":101,"credit_html":135,"title":136,"description":137,"author":113,"original_width":138,"original_height":139},36694,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500490","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500490\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Queensland, Australia) 1 (29804284781).jpg","\u003Cp>Precious opal (\"boulder opal') from Australia. (CIS 212-148, Cranbrook Institute of Science collection, Bloomfield Hills, Michigan, USA)\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 over 4900 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>Opal is hydrous silica (SiO2·nH2O).  Technically, opal is not a mineral because it lacks a crystalline structure.  Opal is supposed to be called a mineraloid.  Opal is made up of extremely tiny spheres (colloids - <a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\">https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\u003C\u002Fa>\" rel=\"nofollow\">www.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg<\u002Fa>) that can be seen with a scanning electron microscope (SEM).\n\u003C\u002Fp>\u003Cp>Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence).  This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids.  Different opalescent colors are produced by colloids of differing sizes.  If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced.  Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).\n\u003C\u002Fp>\u003Cp>Not all opals have the famous play of colors, however.  Common opal has a wax-like luster & is often milky whitish with no visible color play at all.  Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.\n\u003C\u002Fp>\u003Cp>Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians.  Some organisms incorporate opal into their tissues, for example horsetails\u002Fscouring rushes and sawgrass.  Sometimes, fossils are preserved in opal or precious opal.\n\u003C\u002Fp>\u003Cp>Locality: unrecorded locality in Queensland, Australia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of opal:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3004<\u002Fa>\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>References cited:\n\u003C\u002Fp>\nCarr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program.  Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51.  68 pp.",2640,1878,{"id":141,"source_url":142,"license_code":101,"credit_html":143,"title":144,"description":145,"author":113,"original_width":146,"original_height":147},36695,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500493","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500493\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Queensland, Australia) 2 (29804300001).jpg","\u003Cp>Precious opal (\"boulder opal') from Australia. (CIS 212-148, Cranbrook Institute of Science collection, Bloomfield Hills, Michigan, USA)\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 over 5100 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>Opal is hydrous silica (SiO2·nH2O).  Technically, opal is not a mineral because it lacks a crystalline structure.  Opal is supposed to be called a mineraloid.  Opal is made up of extremely tiny spheres (colloids - <a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\">https:\u002F\u002Fwww.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg\u003C\u002Fa>\" rel=\"nofollow\">www.uwgb.edu\u002Fdutchs\u002Facstalks\u002Facscolor\u002FOPALSPHR.jpg<\u002Fa>) that can be seen with a scanning electron microscope (SEM).\n\u003C\u002Fp>\u003Cp>Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence).  This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids.  Different opalescent colors are produced by colloids of differing sizes.  If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced.  Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).\n\u003C\u002Fp>\u003Cp>Not all opals have the famous play of colors, however.  Common opal has a wax-like luster & is often milky whitish with no visible color play at all.  Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.\n\u003C\u002Fp>\u003Cp>Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians.  Some organisms incorporate opal into their tissues, for example horsetails\u002Fscouring rushes and sawgrass.  Sometimes, fossils are preserved in opal or precious opal.\n\u003C\u002Fp>\u003Cp>Locality: unrecorded locality in Queensland, Australia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of opal:\n<a href=\"\u003Ca rel=\"nofollow\" class=\"external free\" href=\"http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\">http:\u002F\u002Fwww.mindat.org\u002Fgallery.php?min=3004\u003C\u002Fa>\" rel=\"nofollow\">www.mindat.org\u002Fgallery.php?min=3004<\u002Fa>\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>References cited:\n\u003C\u002Fp>\nCarr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program.  Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51.  68 pp.",2747,1931,{"id":149,"source_url":150,"license_code":101,"credit_html":151,"title":152,"description":145,"author":113,"original_width":153,"original_height":154},36696,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500605","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=84500605\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Queensland, Australia) 5 (34556890235).jpg",2703,2372,{"id":156,"source_url":157,"license_code":101,"credit_html":158,"title":159,"description":160,"author":113,"original_width":161,"original_height":162},36701,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=96292467","James St. John, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=96292467\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Precious opal (Queensland, Australia) 7.jpg","Precious opal (\"boulder opal') from Australia. (~5.2 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>Opal is hydrous silica (SiO2·nH2O).  Technically, opal is not a mineral because it lacks a crystalline structure.  Opal is supposed to be called a mineraloid.  Opal is made up of extremely tiny spheres that can be seen with a scanning electron microscope (SEM).\n\u003C\u002Fp>\u003Cp>Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence).  This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids.  Different opalescent colors are produced by colloids of differing sizes.  If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced.  Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).\n\u003C\u002Fp>\u003Cp>Not all opals have the famous play of colors, however.  Common opal has a wax-like luster & is often milky whitish with no visible color play at all.  Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.\n\u003C\u002Fp>\u003Cp>Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians.  Some organisms incorporate opal into their tissues, for example horsetails\u002Fscouring rushes and sawgrass.  Sometimes, fossils are preserved in opal or precious opal.\n\u003C\u002Fp>\u003Cp>Locality: unrecorded locality in Queensland, Australia\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Photo gallery of opal:\nwww.mindat.org\u002Fgallery.php?min=3004\n\u003C\u002Fp>\n\u003Chr>\n\u003Cp>Reference cited:\n\u003C\u002Fp>\nCarr et al. (1979) - Andamooka opal fields: the geology of the precious stones field and the results of the subsidised mining program.  Geological Survey of South Australia Department of Mines and Energy Report of Investigations 51.  68 pp.",2555,2181,{"id":164,"source_url":165,"license_code":91,"credit_html":166,"title":167,"description":168,"author":169,"original_width":170,"original_height":170},18166,"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=157394255","W.carter, via \u003Ca href=\"https:\u002F\u002Fcommons.wikimedia.org\u002F?curid=157394255\" rel=\"noopener\">Wikimedia Commons\u003C\u002Fa>","Veins of opal in a boulder opal.jpg","Veins of opal in a dark boulder opal. Studio photography in Vibble, Visby, Gotland, Sweden.","W.carter",2832,[],[173],"Queensland Opal",[],{"history":8,"applications":8}]