{{infobox mineral | name = Idrialite | category = Organic mineral | image = Idrialite-172289.jpg | caption = Idrialite, Skaggs Springs Mine, Sonoma County, California (size: 6.3 x 4.1 x 1.8 cm | formula = C<sub>22</sub>H<sub>14</sub> | IMAsymbol = Id<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 10.BA.20 | dana = 50.03.08.01 | system = Orthorhombic <br/>Unknown space group | symmetry = | unit cell = a = 8.07, b = 6.42 <br/>c = 27.75&nbsp;[Å]; Z&nbsp;=&nbsp;4 | color = Greenish yellow, light brown, colorless | colour = | habit = | twinning = | cleavage = {001}, perfect; {100}, poor | fracture = Conchoidal | tenacity = | mohs = 1.5 | luster = Vitreous to adamantine | streak = | diaphaneity = | gravity = 1.236 | density = | polish = | opticalprop = Biaxial (+) | refractive = n<sub>α</sub>= 1.557 n<sub>β</sub> = 1.734 n<sub>γ</sub> = 2.07 | birefringence = | pleochroism = X = pale yellow; Y = Z = yellow | 2V = 84° | dispersion = | extinction = | length fast/slow = | fluorescence = Short UV=blue, orange, yellow, green white | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = <ref name=HBM.idrialite/><ref name=webmin.idrialite/><ref name=mindat.idrialite/> }} '''Idrialite''' is a rare hydrocarbon mineral with approximate chemical formula C<sub>22</sub>H<sub>14</sub>.<ref name=HBM.idrialite/><ref name=webmin.idrialite/><ref name=mindat.idrialite/>

Idrialite usually occurs as soft orthorhombic crystals, is usually greenish yellow to light brown in color with bluish fluorescence. It is named after Idrija, town in Slovenia, where its occurrence was first described.<ref name=mindat.idrialite/>

The mineral has also been called '''idrialine''', and '''''branderz''''' in German It has also been called '''inflammable cinnabar''' due to its combustibility and association with cinnabar ores in the source locality.<ref name=egle1889/> A mineral found in the Skaggs Springs location of California was described in 1925 and named '''curtisite''', but was eventually found to consist of the same compounds as idrialite, in somewhat different amounts.<ref name=wise1986/><ref name=blum1975/> Thus curtisite is now considered to be merely a variety of idrialite.<ref name=mindat.curtisite/>

==Discovery and occurrence== Idrialite was first described in 1832 for an occurrence in the Idrija region west of Ljubljana, northwestern Slovenia,<ref name=mindat.idrialite/> mixed with clay, pyrite, quartz and gypsum associated with cinnabar.<ref name=HBM.idrialite/>

It also occurs at the Skaggs Springs location in Sonoma County, in western Lake County, and in the Knoxville Mine in Napa County, California.<ref name=HBM.idrialite/> It has also been reported from localities in France, Slovakia and Ukraine.<ref name=mindat.idrialite/>

In the Skaggs Springs occurrence, the mineral occurs in a hot spring area of the Franciscan formation, around a vent in the sandstone that gave off flammable gases. The mineral was described in 1925 and named "curtisite" after the local resident L. Curtis who called attention to it.<ref name=wrig1925/><ref name=wrig1930/> The crystals are square or six sided flakes, 1 mm in diameter, yellow to pistachio green in transmitted light. It is associated with opaline silica, realgar (arsenic sulfide) and metacinnabarite (mercuric sulfide), which had been deposited in that order before it.<ref name=wrig1930/>

==Composition and properties== The Curtisite variety is only slightly soluble in hot acetone, amyl acetate, butanol, petroleum ether. The solubility is 0.5% or less in hot carbon bisulfide, carbon tetrachloride, chloroform, diethyl ether, or boiling benzene; about 1.5% in toluene, about 2.5% in xylene, and over 10% in hot aniline. The material purified by repeated recrystallization melts at 360-370 C while turning very black. It sublimes giving very thin iridescent colors.<ref name=wrig1930/>

Raman spectroscopy studies indicate that it may be a mixture of complex hydrocarbons including benzonaphthothiophenes (chemical formula: C<sub>16</sub>H<sub>10</sub>S) and dinaphthothiophenes (chemical formula: C<sub>20</sub>H<sub>12</sub>S).<ref name=Frank/>

Curtisite and idrialite have been found to be unique complex mixtures of over 100 polyaromatic hydrocarbons (PAHs) consisting of six specific PAH structural series with each member of a series differing from the previous member by addition of another aromatic ring. The curtisite and idrialite samples contained many of the same components but in considerably different relative amounts.<ref name=wise1986/><ref name=geis1967/>

The major PAH constituents of the curtisite sample were: picene (a PAH with 5 fused benzene rings), [[dibenzo(a,h)fluorene|dibenzo[a,h]fluorene]], [[11H-indeno(2,1-a)phenanthrene|11H-indeno[2,1-a]phenanthrene]], [[benzo(b)phenanthro(2,1-d)thiophene|benzo[b]phenanthro[2,1-d]thiophene]], indenofluorenes, chrysene, and their methyl- and dimethyl-substituted homologues; the major components in the idrialite sample were higher-molecular-weight PAH, i.e. benzonaphthofluorenes (molecular weight 316), benzoindenofluorenes (MW 304) and benzopicene (MW 328), in addition to the compounds found in the curtisite sample.<ref name=wise1986/>

Curtisite is also associated with small amounts of a dark brown oil, that appears to be responsible for some of the yellow color and most of the fluorescence, and can be separated by recrystallization.<ref name=wrig1930/>

Based on the composition, it was conjectured that the compounds were produced by medium-temperature pyrolysis of organic matter, then further modified by extended equilibration at elevated temperatures in the subsurface and by recrystallization during migration.<ref name=blum1975/>

When distilled, it produces the mineral wax idrialin.<ref name=thom1838/><ref name=gold1879/>

==References== <references>

<ref name=mindat.curtisite>"[https://www.mindat.org/min-26563.html Curtisite]" page at the Mindat.org online database. Accessed on 2020-08-28.</ref>

<ref name=mindat.idrialite>"[https://www.mindat.org/min-26563.html Idrialite]" page at the Mindat.org online database. Accessed on 2020-08-28.</ref>

<ref name=webmin.idrialite>Dave Barthelmy (2012): "[http://webmineral.com/data/Idrialite.shtml Idrialite Mineral Data]". Online document at Webmineral.com. Accessed on 2020-08-28.</ref>

<ref name=wrig1925>F. E. Wright and E. T. Allen (1925): "Curtisite, a new organic mineral from Skaggs Springs, Sonoma County, California (abstract)" ''American Mineralogist'', volume 11, pages 67-67.</ref>

<ref name=wrig1930>F. E. Wright and E. T. Allen (1930): "[https://pubs.geoscienceworld.org/msa/ammin/article-abstract/15/5/169/535605/ Curtisite, a new organic mineral from Skaggs Springs, Sonoma County, California]". ''American Mineralogist'', volume 15, pages 169-173.</ref>

<ref name=geis1967>T. A. Geissman, K. Y. Sun, and J. Murdoch (1967): "Organic minerals. Picine and chrysene as constituents of the mineral Curtisite (idrialite)". ''Experentia'', volume 23, pages 793-794.</ref>

<ref name=HBM.idrialite>"[http://www.handbookofmineralogy.org/pdfs/idrialite.pdf Idrialite]{{Dead link|date=August 2025 |bot=InternetArchiveBot |fix-attempted=yes }}" entry in John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, and Monte C. Nichols (): ''[http://www.handbookofmineralogy.org/ Handbook of Mineralogy]''. Published by the Mineralogical Society of America. Accessed on 2020-08-28</ref>

<ref name=Frank>{{cite journal|last1=Frank|first1=Otakar|last2=Jehlička|first2=Jan|last3=Edwards|first3=Howell G.M.|title=Raman spectroscopy as tool for the characterization of thio-polyaromatic hydrocarbons in organic minerals|journal=Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy|date=December 2007|volume=68|issue=4|pages=1065–1069|doi=10.1016/j.saa.2006.12.033|pmid=17307383|bibcode=2007AcSpA..68.1065F}}</ref>

<ref name=blum1975>Max Blumer (1975): "Curtisite, idrialite and pendletonite, polycyclic aromatic hydrocarbon minerals: Their composition and origin" ''Chemical Geology'', volume 16, issue 4, pages 245-256. {{doi|10.1016/0009-2541(75)90064-9}}</ref>

<ref name=wise1986>Stephen A. Wise, Robert M. Campbell, W. Raymond West, Milton L. Lee, Keith D. Bartle (1986): "Characterization of polycyclic aromatic hydrocarbon minerals curtisite, idrialite and pendletonite using high-performance liquid chromatography, gas chromatography, mass spectrometry and nuclear magnetic resonance spectroscopy". ''Chemical Geology'', volume 54, issues 3–4, pages 339-357. {{doi|10.1016/0009-2541(86)90148-8}}</ref>

<ref name=egle1889>{{Cite book|url=https://books.google.com/books?id=irnETdF9eIgC&pg=PA83|title=Catalogue of Minerals and Synonyms|last=Egleston|first=Thomas|date=1889|publisher=U.S. Government Printing Office|pages=83|language=en}}</ref>

<ref name=thom1838>{{Cite book|url=https://books.google.com/books?id=QBdPdPaOQKMC&pg=PA749|title=Chemistry of Organic Bodies: Vegetables|last=Thomson|first=Thomas|date=1838|publisher=Maclachlan & Stewart|pages=748|language=en}}</ref>

<ref name=gold1879>{{Cite book|url=https://books.google.com/books?id=QbZLAAAAYAAJ&pg=PA167|title=Journal of the Chemical Society|last=Goldschmidt|first=G.|publisher=The Chemical Society of Great Britain|year=1879|editor-last=Watts|editor-first=Henry|pages=167|language=en}}</ref>

</references>

{{Commons}}

Category:Organic minerals Category:Orthorhombic minerals Category:Luminescent minerals Category:Minerals described in 1832 Category:Idrija