Parnauite

{{Infobox mineral | name = Parnauite | boxwidth = | boxbgcolor = #228B22 | image = Parnauite-89334.jpg | caption = Parnauite | category = Arsenate minerals | formula = Cu₉(AsO₄)₂(SO₄)(OH)₁₀ · 7H₂O | IMAsymbol = Pna | molweight = | strunz = 8.DF.35 | dana = 43.5.13.1 | system = Orthorhombic | unit cell = 641.15 ų (calculated) | color = Pale blue, green, dark green, blue-green, yellow-green | habit = Fans and rosettes of lath-like crystals; fibrous; scaly crusts | cleavage = Good | mohs = 2 | streak = Greenish white | gravity = 3.09 | opticalprop = Biaxial (−) | refractive = nα = 1.680(3), nβ = 1.704(3), nγ = 1.712(3) | birefringence = δ = 0.032 | pleochroism = Weak | 2V = Measured: 60°(5); calculated: 58° | dispersion = r > v (strong) | extinction = Optic plane parallel to {100}.<br/>X = b, Y = a, Z = c. | length fast/slow = | fluorescence = None | impurities = P, C, Al | references = <ref name="Webmineral">{{cite web |title=Parnauite Mineral Data |url=https://webmineral.com/data/Parnauite.shtml |website=Webmineral |access-date=13 December 2025}}</ref> }}

'''Parnauite''' is a very rare secondary copper arsenate–sulfate mineral.<ref name="HoM">{{cite web |title=Parnauite (Handbook of Mineralogy) |publisher=Mineral Data Publishing |url=https://rruff.info/doclib/hom/parnauite.pdf |access-date=13 December 2025}}</ref> It forms near the Earth's surface in oxidized zones of various copper deposits. These copper minerals are altered by oxygen-rich water and new minerals grow as a thin coatings or small crystal clusters.<ref name="HoM" /> Parnauite is typically blue-green to green and commonly occurs as tiny bladed crystals in fan-shaped sprays or rosettes. It may also appear as scaly crusts or crystal-like surface films.<ref name="Mindat">{{cite web |title=Parnauite: Mineral information, data and localities |website=Mindat.org |url=https://www.mindat.org/min-3124.html |access-date=13 December 2025}}</ref>

== Discovery == Parnauite was discovered in 1978 from the Majuba Hill Mine (Antelope Mining District), Pershing County, Nevada.<ref name="Wise1978">{{cite journal |last=Wise |first=William S. |year=1978 |title=Parnauite and goudeyite, two new copper arsenate minerals from the Majuba Hill Mine, Pershing County, Nevada |journal=American Mineralogist |volume=63 |issue=7–8 |pages=704–708}}</ref> Another new copper arsenate, Goudeyite was also discovered from the same location. This shows that oxidation at Majuba Hill produces an unusually diverse set of secondary copper minerals.<ref name="Wise1978" />

Parnauite was named in honour of U.S. mineral collector John L. "Jack" Parnau. He is credited with collecting many different minerals from Majuba Hill that were later studied and found to be completely new minerals.<ref name="HoM">{{cite web |title=Parnauite (Handbook of Mineralogy) |publisher=Mineral Data Publishing |url=https://rruff.info/doclib/hom/parnauite.pdf |access-date=13 December 2025}}</ref>

Parnauite is also in institutional collections, including the University of California, Santa Barbara, California, and the National Museum of Natural History, Smithsonian Institution in Washington, DC.<ref name="HoM" />

Majuba Hill's lithology is composed of small igneous intrusions, often described as a volcanic plugs. It's made up of porphyritic rhyolite and several types of breccia. These minerals helps explain why parnauite forms there. These igneous intrusions were emplaced into older sedimentary strata that is largely made up of shale.<ref name="USGS_pub">{{cite web |title=Tin, copper, and uranium at Majuba Hill, Nevada |website=U.S. Geological Survey |url=https://www.usgs.gov/publications/tin-copper-and-uranium-majuba-hill-nevada |access-date=13 December 2025}}</ref>

The deposit contains copper and tin mineralization. In many parts of the mine, the ore is strongly oxidized, meaning the original ore minerals have been chemically altered by oxygen-rich water near the surface. This oxidation produces a wide range of secondary copper minerals.<ref name="USGS_report">{{cite report |title=Tin, copper, and uranium at Majuba Hill, Nevada |publisher=U.S. Geological Survey |series=Trace Elements Investigations Report |number=81A |url=https://pubs.usgs.gov/tei/081a/report.pdf |access-date=13 December 2025}}</ref>

== Chemistry and properties == Parnauite is a hydrated copper arsenate–sulfate with the formula Cu₉(AsO₄)₂(SO₄)(OH)₁₀·7H₂O.<ref name="HoM" /> It is made mostly of copper, with arsenic and sulfur bound into oxygen-rich groups, hydroxides, and water molecules.

Under polarized light, parnauite is biaxial negative with weak pleochroism (a slight color change with viewing direction).<ref name="HoM" /> Because fibrous parnauite can resemble other blue-green secondary copper minerals, identification often requires laboratory testing such as X-ray diffraction.<ref name="Mills2013">{{cite journal |last1=Mills |first1=Stuart J. |last2=Kampf |first2=Anthony R. |last3=McDonald |first3=Andrew M. |last4=Bindi |first4=Luca |last5=Christy |first5=Andrew G. |last6=Kolitsch |first6=Uwe |last7=Favreau |first7=Georges |year=2013 |title=The crystal structure of parnauite: a copper arsenate–sulphate with translational disorder of structural rods |journal=European Journal of Mineralogy |volume=25 |issue=4 |pages=693–704 |doi=10.1127/0935-1221/2013/0025-2329 |bibcode=2013EJMin..25..693M }}</ref>

== Extent == Parnauite is very rare and is known only in a relatively small number of locations worldwide.<ref name="HoM" /> Reported occurrences include:

* Majuba Hill Mine, the Burrus Mine, Nevada * Grandview Mine, Arizona. * Small amounts in Colorado and Utah * Cap Garonne mine in France * varies locations in the Black Forest in Germany * Clara Mine in Ľubietová, Slovakia * The Tynagh mine in County Galway, Ireland * Several mines in Cornwall and Wales * Tsumeb area in Namibia.

''Reference'':<ref name="HoM" />

== References == {{reflist}}

Category:Copper minerals Category:Arsenate minerals Category:Sulfate minerals Category:Minerals in space group 31