{{Short description|Sorosilicate mineral}} {{Infobox mineral | name = Junitoite | category = Sorosilicate | image = File:Junitoite-744478.jpg | imagesize = 260px | caption = Vitreous to pearly junitoite crystals to 4 mm from the Christmas Mine in Gila County, Arizona | formula = CaZn<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>·H<sub>2</sub>O | IMAsymbol = Jit<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|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|url-access=subscription}}</ref> | molweight = | strunz = 9.BD.15 | dana = 56.2.1.1 | system = Orthorhombic | class = Pyramidal (mm2) <br/>H-M group: (mm2) | symmetry = ''A''ma2<ref name=handbook/> | unit cell = a = 12.510(7) <br/>b = 6.318(3) <br/>c = 8.561(6) [Å]; Z = 4<ref name=handbook/> | color = Colorless, milk-white, or colored due to alteration<ref name=handbook/> | habit = | twinning = | cleavage = Good on {100}; poor on {010} and {011} | fracture = Micaceous | tenacity = Brittle to semi-sectile due to alteration<ref name=handbook/> | mohs = 4.5 | luster = Adamantine, Vitreous, Sub-Vitreous | polish = | refractive = n<sub>α</sub> = 1.656<br>n<sub>β</sub> = 1.664<br>n<sub>γ</sub> = 1.672 | opticalprop = Biaxial (+) | birefringence = δ = 0.016 | 2V = Measured: 86°, Calculated: 88° | dispersion = | pleochroism = | fluorescence= | absorption = | streak = Colorless | gravity = | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent<ref name=handbook/> | other = | references =<ref name=mindat>{{cite web|title=Junitoite|url=http://www.mindat.org/min-2123.html|publisher=Mindat|access-date=December 2, 2012}}</ref> }} '''Junitoite''' is a mineral with formula CaZn<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>·H<sub>2</sub>O. It was discovered at the Christmas mine in Christmas, Arizona, and described in 1976. The mineral is named for mineral chemist Jun Ito (1926–1978).
==Description and occurrence== Junitoite is transparent to translucent and is colorless, milk-white, or colored due to alteration. Crystals grow up to {{convert|5|mm|in}} and have high quality faces.<ref name=handbook/>
Junitoite occurs in fractures through pods of sphalerite. It formed by retrograde metamorphism and oxidation of tactite, also resulting in kinoite.<ref name=handbook/>{{sfn|Williams|1976|p=1255}}{{sfn|Hamilton|Finney|1985|p=91}} The mineral is known from New Jersey and the type locality in Arizona.<ref name=mindat/> Junitoite occurs in association with apophyllite, calcite, kinoite, smectite, and xonotlite.<ref name=handbook>{{cite encyclopedia|url=http://www.handbookofmineralogy.org/pdfs/junitoite.pdf |title=Junitoite |encyclopedia=Handbook of Mineralogy |editor1-first=John W. |editor1-last=Anthony|editor2-first=Richard A. |editor2-last=Bideaux|editor3-first=Kenneth W. |editor3-last=Bladh|editor4-first= Monte C. |editor4-last=Nichols |publisher=Mineralogical Society of America|location=Chantilly, VA}}</ref>
==Crystal structure== left|thumb|Crystal structure of junitoite. Gray – Ca, green – Ow5, blue – H, yellow – ZnO<sub>4</sub>, purple – SiO<sub>4</sub> In 1968, Jun Ito published the results of synthesis of various lead calcium zinc silicates. The formula of one phase, designated ''X<sub>3</sub>'', was identified as probably CaZnSi<sub>2</sub>O<sub>6</sub>·H<sub>2</sub>O.<ref>{{cite journal|last=Ito|first=Jun|title=Synthesis of some lead calcium zinc silicates|journal=American Mineralogist|date=January–February 1968|volume=53|issue=1–2|url=http://www.minsocam.org/ammin/am53/am53_231.pdf|page=231}}</ref> When he described junitoite, Sidney Williams identified the mineral's formula as CaZn<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>·H<sub>2</sub>O, based on communications with Ito.{{sfn|Williams|1976|p=1255}}{{sfn|Williams|1976|p=1258}}
The mineral's crystal structure was first determined in 1985 and refined in 2012.{{sfn|Hamilton|Finney|1985|p=91}}{{sfn|Yang|Jenkins|Downs|2012|p=i73}} The mineral crystallizes in the orthorhombic crystal system.<ref name=handbook/> The structure is formed by chains of corner-sharing ZnO<sub>4</sub> tetrahedra linked together by Si<sub>2</sub>O<sub>7</sub> tetrahedral pairs. Calcium ions occupy vacancies and coordinate to five oxygen atoms and one water molecule.{{sfn|Yang|Jenkins|Downs|2012|p=sup-1}}
==History== The first known specimen of junitoite was collected from the Christmas mine at Christmas, Arizona, and entered the collection of Joe Ana Ruiz. Geologist Robert A. Jenkins noticed the mineral in kinoite specimens, submitting Ruiz's sample to Sidney A. Williams for study. Further samples came from the collections of Ruiz and Raymond Diaz.{{sfn|Williams|1976|p=1255}}
Williams identified the specimens as a new mineral and described it in the journal ''American Mineralogist'' in 1976. He named it ''junitoite'' in honor of Jun Ito, the mineral chemist who noted the compound of which the mineral is composed.{{sfn|Williams|1976|p=1258}} The International Mineralogical Association approved the mineral as IMA 1975-042.<ref name=IMA2012>{{cite web|title=The New IMA List of Minerals – A Work in Progress – Update: November 2012|url=http://pubsites.uws.edu.au/ima-cnmnc/IMA_Master_List_(2012-11).pdf|work=Commission on New Minerals, Nomenclature and Classification|publisher=International Mineralogical Association|access-date=December 18, 2012|page=83}}</ref> The type material is housed in the University of Arizona, Harvard University, the National Museum of Natural History, the University of Paris, the National School of Mines, and The Natural History Museum.<ref name=handbook/>
==References== {{Reflist|30em}}
;Bibliography *{{cite journal|last1=Hamilton|first1=R. D.|last2=Finney|first2=J. J.|title=The structure of junitoite, CaZn<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>·H<sub>2</sub>O|journal=Mineralogical Magazine|date=March 1985|volume=49|issue=350|pages=91–95|url=http://www.minersoc.org/pages/Archive-MM/Volume_49/49-350-91.pdf|doi=10.1180/minmag.1985.049.350.13|bibcode=1985MinM...49...91H|s2cid=140636176 }} *{{cite journal|last=Williams|first=Sidney A.|title=Junitoite, a new hydrated calcium zinc silicate from Christmas, Arizona|journal=American Mineralogist|date=November–December 1976|volume=61|issue=11–12|pages=1255–1258|url=http://www.minsocam.org/ammin/AM61/AM61_1255.pdf}} *{{cite journal|last1=Yang|first1=Hexiong|last2=Jenkins|first2=Neil G.|last3=Downs |first3=Robert T.|title=Redetermination of junitoite, CaZn<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>·H<sub>2</sub>O|journal=Acta Crystallographica Section E|year=2012|volume=E68|issue=10|url=http://rruff.info/uploads/ACE68_i73.pdf|doi=10.1107/S1600536812037622|pmc=3470120|pmid=23125564|page=i73}}
==External links== {{commons category|Junitoite}} *[http://www.mindat.org/gallery.php?min=2123 Images of junitoite] from mindat.org
Category:Calcium minerals Category:Zinc minerals Category:Hydrates Category:Sorosilicates Category:Orthorhombic minerals Category:Minerals in space group 40
Category:Minerals described in 1976