{{Short description|Nesosilicate mineral}} {{Infobox mineral | name = Willemite | category = Silicate mineral | boxwidth = | boxbgcolor = | image = File:Willemite-168225.jpg | imagesize = | caption = Willemite from Namibia | formula = {{chem2|Zn2SiO4}} | IMAsymbol = Wlm<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 = 9.AA.05 (10 ed) <br/><small>8/A.01-20 (8 ed)</small> | dana = 51.1.1.2 | system = Trigonal | class = Rhombohedral ({{overline|3}}) <br /><small> (same H-M symbol)</small> | symmetry = ''R''{{Overline|3}} | color = Colorless to white, gray, black, flesh-red, burgundy-red, pink, brown, dark brown, mahogany-brown, honey-yellow, yellow, apple-green, blue, pastel green, light blue, azure-blue | habit = Fibrous, botryoidal to massive | twinning = | cleavage = {0001}, {11{{Overline|2}}0} – imperfect | fracture = Irregular to conchoidal | mohs = 5.5 | luster = Vitreous to resinous | refractive = nω = 1.691{{snd}}1.694 nε = 1.719{{snd}}1.725 | opticalprop = Uniaxial (+) | birefringence = δ = 0.028 | pleochroism = | streak = | gravity = 3.9{{snd}}4.2 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to opaque | other = Strongly fluorescent; may be phosphorescent | var1 = troostite | var1text = zinc is partly replaced by manganese | references = <ref name=Handbook>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Willemite |url=http://www.handbookofmineralogy.org/pdfs/willemite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=23 July 2022 |date=2005}}</ref><ref name=Mindat>{{mindat|id=4292|title=Willemite|access-date=23 July 2022}}</ref><ref name=Webmineral>{{Cite web|last1=Barthelmy|first1=David|year=2014|url=http://www.webmineral.com/data/Willemite.shtml|access-date=23 July 2022|title = Willemite Mineral Data|website=Webmineral.com}}</ref>}}
'''Willemite''' is a zinc silicate mineral ({{chem2|Zn2SiO4}}) and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. '''Troostite''' is a variant in which part of the zinc is partly replaced by manganese, it occurs in solid brown masses.
It was discovered in 1829 in the Belgian Vieille-Montagne mine. Armand Lévy was shown samples by a student at the university where he was teaching. Lévy named it after William I of the Netherlands<ref>{{cite journal |last1=Denayer |first1=Julien |display-authors=etal |title=Les sciences géologiques à l'Université de Liège : deux siècles d'évolution Partie 1 : de la fondation à la Première Guerre Mondiale |journal=Bulletin de la Société Royale des Sciences de Liège |date=2017 |volume=86 |doi=10.25518/0037-9565.7303 |s2cid=134239255 |url=https://popups.uliege.be/0037-9565/index.php?id=7303#tocto2n3 |language=fr |issn=0037-9565 |quote=En 1829, [Armand Lévy] décrivit la willémite [...], nouvelle espèce minérale découverte à la Vieille-Montagne à Moresnet, et la dédia à Guillaume (Willem) 1<sup>er</sup> des Pays-Bas (Lévy, 1830; Lacroix, 1919; Buttgenbach, 1947a). « Ce minéral, très-abondant à Moresnet, avait échappé à l’attention des minéralogistes qui avaient visité cette localité, lorsqu’un élève de l’université de Liége en apporta plusieurs morceaux qui me parurent appartenir à une espèce différente de celles que je connaissais; en conséquence je me rendis sur les lieux, et, après avoir mûrement examiné les nombreux échantillons que j’y rencontrai, je fus convaincu que ma conjecture était fondée » (Lévy, 1843).|doi-access=free }} (Translation: "In 1829, [Lévy] described willemite, a new mineral discovered at Moresnet's Vieille-Montagne and dedicated to William I of the Netherlands. "The mineral—quite abundant in Moresnet—went unnoticed by mineralogists who had visited this location. A student of the University of Liège brought me several pieces that I was unfamiliar with, so I went to these places. After carefully examining the many samples that I came across, I was convinced that my supposition was founded.")</ref> (it is occasionally spelled '''villemite''').<ref>See: * {{cite journal |last1=Levy |first1=A. |title=Lüttich, 14. September 1829 |journal=Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde |date=1830 |volume=1 |page=71 |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015006998226&view=1up&seq=91 |language=German}} From p. 71: ''"Bei einer Exkursion, welche ich neulich gemacht, glaube ich ein neues Mineral entdeckt zu haben; es soll Willemite heissen, nach S.M. dem König der Niederlande."'' (During an excursion which I made recently, I believe that I discovered a new mineral; it shall be called "Willemite", after His Majesty the King of the Netherlands.) * {{cite book |last1=Chester |first1=Albert Huntington |title=A Dictionary of the Names of Minerals Including Their History and Etymology |date=1896 |publisher=John Wiley & Sons |location=New York City, New York, USA |page=[https://archive.org/details/adictionaryname00chesgoog/page/n336 288] |url=https://archive.org/details/adictionaryname00chesgoog}}</ref><ref>{{cite book|last=Wurtz|first=Charles Adolphe|title=Dictionnaire de chimie pure et appliquée|url=https://books.google.com/books?id=nDZEAAAAYAAJ&pg=PA722|year=1878|publisher=Hachette|page=722|quote= Syn. '''Wihlemite''', '''williamsite''', troostite. [...] dans les amas de calamine de la Vieille-Montagne}}</ref><ref>{{cite book|title=Bulletin de Minéralogie|url=https://books.google.com/books?id=51whAQAAIAAJ|year=1919|publisher=Masson|language=fr|page=127|quote= Ainsi s'explique qu'en 1829 il ait dédié au roi des Pays-Bas, Wilhem I, la '''villemite''', qu'il venait de découvrir à la Vieille-Montagne.}} ("[...] in 1829 he dedicated to the king of the Netherlands, William I, the '''villemite''', which he had just discovered at Vieille-Montagne.")</ref> The troostite variety is named after Dutch-American mineralogist Gerard Troost.<ref>{{Merriam-Webster|troostite}}</ref>
==Occurrence== [[File:Willemite 2 variety troostite zinc orthosilicate Franklin Sussex County New Jersey 1907.jpg|thumb|left|160px|Willemite variety troostite from New Jersey]] Willemite is usually formed as an alteration of previously existing sphalerite ore bodies, and is usually associated with limestone. It is also found in marble and may be the result of a metamorphism of earlier hemimorphite or smithsonite.<ref>Klein, Cornelis (2007). ''The Manual of Mineral Science'', p.484. John Wiley and Sons, Inc., Hoboken. {{ISBN|9780471721574}}.</ref> Crystals have the form of hexagonal prisms terminated by rhombohedral planes: there are distinct cleavages parallel to the prism-faces and to the base. Granular and cleavage masses are of more common occurrence.<ref name="EB1911">{{EB1911|inline=y|wstitle=Willemite|volume=28|page=658|first=Leonard James|last=Spencer|authorlink=Leonard James Spencer}}</ref> It occurs in many places, but is best known from Arizona and the zinc, iron, manganese deposits at Franklin and Sterling Hill Mines in New Jersey. It often occurs with red zincite (zinc oxide) and franklinite ({{chem2|Fe,Mn,Zn)(Fe,Mn)2O4}} (an iron rich zinc mineral occurring in sharp black isometric octahedral crystals and masses). Franklinite and zincite are not fluorescent.
==Uses== Artificial willemite was used as the basis of first-generation fluorescent tube phosphors. When doped with manganese ions, it fluoresces with a broad white emission band. Some versions had some of the zinc replaced with beryllium. In the 1940s it was largely replaced by second-generation halophosphors based on fluorapatite. These, in turn have been replaced by the third-generation TriPhosphors.<ref>{{cite web | url = http://home.frognet.net/~ejcov/thayer.html | title = The Fluorescent Lamp: Early U. S. Development | first = R. N. | last = Thayer}}</ref><ref>{{cite book | chapter = A Review of Early Inorganic Phosphors | chapter-url =https://books.google.com/books?id=klE5qGAltjAC&pg=PA98 | page = 98 | title = Revolution in lamps: a chronicle of 50 years of progress | isbn = 978-0-88173-378-5 | author1 = Kane, Raymond | author2 = Sell, Heinz | year = 2001 }}</ref><!--https://books.google.com/books?id=JuBSAAAAMAAJ&q=zinc+beryllium+silicate&dq=zinc+beryllium+silicate&hl=en&ei=BoqsTZHoHYTEsgaErZWcCA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDYQ6AEwAjgU--> left|350px|thumb|Crystal structure of willemite
center|thumb|700px|In natural and in ultraviolet light
==See also== *List of minerals *List of minerals named after people
==References== {{Reflist}}
==External links== *{{Commons category-inline}}
Category:Nesosilicates Category:Zinc minerals Category:Trigonal minerals Category:Minerals in space group 148 Category:Luminescent minerals Category:Minerals described in 1829