{{Short description|Secondary zinc carbonate mineral}} {{Infobox mineral | name = Brianyoungite | category = Carbonate mineral | image = Brianyoungite-122711.jpg | imagesize = 260px | caption = Brianyoungite from Germany | formula = Zn<sub>3</sub>(CO<sub>3</sub>,SO<sub>4</sub>)(OH)<sub>4</sub><ref name=IMA/> | IMAsymbol=Byo<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> | strunz = 5.BF.30 (10 ed) <br/><small>5/C.01-105 (8 ed)</small> | dana = 17.1.15 | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''C2/m'' | unit cell = 15.724 Å, <br/>b = 6.256 Å, <br/>c = 5.427 Å; β = 90°; Z = 4 | color = White | habit = Rosettes of thin blades, pseudo-orthorhombic with β close to 90° <ref name="Livingstone1993" /> | twinning = | cleavage = Perfect on {100}, possible on {001}<ref name="Livingstone1993" /><ref name=HOM/> | fracture = | tenacity = | mohs = 2 to 2.5 | luster = Vitreous | refractive = n<sub>ω</sub> = 1.635, n<sub>ε</sub> = 1.650 | opticalprop = Biaxial | birefringence = δ = 1.635<ref name=Mindat/> | pleochroism = | streak = White | gravity = 3.93 to 4.09 | melt = | fusibility = | diagnostic = | solubility = Readily soluble with effervescence in acids<ref name="Livingstone1993" /> | diaphaneity = Transparent to translucent | other = Non-fluorescent<ref name="Livingstone1993" /> | references = <ref name=IMA>{{cite web |url=http://rruff.info/ima |title=IMA Mineral List with Database of Mineral Properties}}</ref><ref name=Webmin>{{cite web |url=http://www.webmineral.com/data/Brianyoungite.shtml#.UkJEjD-H_hU |title=Brianyoungite Mineral Data |publisher=Webmineral.com |date= |accessdate=2013-11-15}}</ref><ref name="Livingstone1993">{{cite journal |last1=Livingstone |first1=A. |last2=Champness |first2=P.E. |title=Brianyoungite, a New Mineral Related to Hydrozincite, from the North of England Orefield |journal=Mineralogical Magazine |volume=57 |issue=389 |year=1993 |pages=665–670 |issn=0026-461X |doi=10.1180/minmag.1993.057.389.10 |bibcode=1993MinM...57..665L |s2cid=54051555 |url=http://www.minersoc.org/pages/Archive-MM/Volume_57/57-389-665.pdf |access-date=2013-11-15 |archive-date=2014-08-09 |archive-url=https://web.archive.org/web/20140809060320/http://www.minersoc.org/pages/Archive-MM/Volume_57/57-389-665.pdf |url-status=dead }}</ref><ref name=HOM>{{cite web |url=http://rruff.info/doclib/hom/brianyoungite.pdf |title=Handbook of Mineralogy |publisher=Handbook of Mineralogy |date= |accessdate=2013-11-15}}</ref><ref name=Mindat>{{cite web |url=http://www.mindat.org/min-772.html |title=Brianyoungite: Brianyoungite mineral information and data |publisher=Mindat.org |date= |accessdate=2013-11-15}}</ref><ref name=Dana>Gaines et al (1997) Dana's New Mineralogy Eighth Edition. Wiley </ref>}}
'''Brianyoungite''' is a secondary zinc carbonate mineral. The Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA) classifies it as a carbonate with the formula {{Chem2|Zn3(CO3)(OH)4}},<ref name=IMA/> but sulfate groups SO<sub>4</sub> also occupy the carbonate CO<sub>3</sub> positions, in the ratio of about one sulfate to three carbonates,<ref name="Livingstone1993" /> so other sources give the formula as {{Chem2|Zn3(CO3,SO4)(OH)4}}, and Gaines et al. classify the mineral as a compound carbonate.<ref name=Dana/> It is similar in appearance to hydrozincite, another zinc carbonate.<ref name=Mindat/> It was discovered in 1991 and designated IMA1991-053.<ref name=Mindat/> In 1993 it was named "brianyoungite" after Brian Young (born 1947), a field geologist with the British Geological Survey, who provided the first specimens.<ref name=HOM/><ref name=Dana/>
== Appearance == thumb|left|Brianyoungite (white) with fluorite and sphalerite from the Brownley Hill Mine, Cumbria, England. The mineral occurs as tiny rosettes less than 100 μm across, composed of thin blades just one or two micrometers across, elongated parallel to the b crystal axis, and tapering to a sharp point.<ref name="Livingstone1993" /> The crystals are white and transparent to translucent, with a vitreous lustre and a white streak.
== Structure == The mineral belongs in the orthorhombic crystal system, or the monoclinic with β (the angle between the a and c crystal axes) close to 90<sup>o</sup>.<ref name="Livingstone1993" /> The space group is unknown, but assumed to be either P2<sub>1</sub>/m, P21 or P2221.<ref name=HOM/><ref name=Mindat/> The structure is similar to that of hydrozincite.<ref name=Dana/> There are four formula units per unit cell (Z = 4) and the lengths of the sides of the unit cell are a = 15.724 Å, b = 6.256 Å and c = 5.427 Å.<ref name="Livingstone1993" />
== Physical properties == Brianyoungite is a soft mineral with Mohs hardness similar to halite, only 2 to {{frac|2|1|2}} according to some sources,<ref name=Webmin/><ref name=Mindat/> but others say that the hardness is not determinable.<ref name="Livingstone1993" /><ref name=HOM/> It is fairly dense, with specific gravity 3.93 to 4.09, similar to that of celestine. Cleavage is perfect perpendicular to the a crystal axis (perfect on {100}) and possible perpendicular to the c crystal axis (possible on {001}).<ref name="Livingstone1993" /><ref name=HOM/> It is readily soluble with effervescence in acids.<ref name="Livingstone1993" />
== Optical properties == The mineral is biaxial, with refractive indices n<sub>ω</sub> = 1.635 and n<sub>ε</sub> = 1.650 and maximum birefringence δ = 1.635.<ref name=Mindat/> It exhibits straight extinction.<ref name="Livingstone1993" /> It is not fluorescent.<ref name="Livingstone1993" />
== Occurrence == The type locality is the Bloomsberry Horse level of the Brownley Hill mine, Nenthead, Alston Moor District, North Pennines, North and Western Region (Cumberland), Cumbria, England.<ref name=Mindat/> The type material is conserved at the Royal Museum of Scotland, Edinburgh, Scotland, 1992.17.1–8.<ref name=HOM/><br /> Brianyoungite occurs with gypsum on rubbly limestone in the oxidised zone of Brownley Hill Mine, and on specimens from the nearby Smallcleugh mine.<ref name="Livingstone1993" /> It may be a secondary post-mining mineral.<ref name=Webmin/><ref name=HOM/> At the type locality it is associated with gypsum, smithsonite, pyrite and goethite.<ref name=HOM/>
==References== {{reflist}}
Category:Zinc minerals Category:Carbonate minerals Category:Monoclinic minerals Category:Minerals in space group 12 Category:Minerals described in 1993