{{Short description|Mineral from the class of hydrous sulfates}} {{Infobox mineral | name = Picromerite | image = Halite-Picromerite-mrz114a.jpg | alt = | caption = Picromerite on halite | category = Sulfate mineral | formula = K<sub>2</sub>Mg(SO<sub>4</sub>)<sub>2</sub>·6H<sub>2</sub>O | IMAsymbol = Pmr<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 = 7.CC.60 | dana = 29.03.06.01 | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''P''2<sub>1</sub>/a | unit cell = a = 9.07, b = 12.21, <br/>c = 6.11&nbsp;[Å]; β = 104,8°; Z&nbsp;=&nbsp;2 | color = Colorless; white, grey, reddish, yellowish | habit = massive aggregates; crusts; prismatic crystals | twinning = | cleavage = perfect {<nowiki/>{{Overline|2}}01}<ref name="Datenblatt" /> | fracture = | tenacity = | mohs = 2.5 | luster = Vitreous | streak = White | diaphaneity = Transparent | gravity = | density = 2.03<ref name="Datenblatt" /> | polish = | opticalprop = Biaxial (+) | refractive = n<sub>α</sub> = 1.461 n<sub>β</sub> = 1.463 n<sub>γ</sub> = 1.476<ref name="Mindat" /> | birefringence = δ = 0.015<ref name="Mindat" /> | pleochroism = | 2V = Measured: 47°<ref name="Mindat" /> | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = in cold water | impurities = | alteration = | other = | prop1 = Taste | prop1text = bitter | references = <ref name="Mindat"/><ref name="Datenblatt"/><ref name="Webmin"/> }} '''Picromerite''' (synonyms: '''schoenite''', '''schönite''') is a mineral from the class of hydrous sulfates lacking additional anions, and containing medium to large cations according to the Nickel–Strunz classification.<ref name="Mindat"/>

== Etymology == The name comes from the Greek words πικρός [pikros] for "bitter" and μέρος [meros] for "part", and relates to the bitter taste of the mineral.

== Occurrence == Picromerite is found on comparatively few places, currently (2015) only about 40 localities are known.<ref name="Mindat" /> It was first identified in active volcanic fumaroles on Mount Vesuvius by Arcangelo Scacchi in 1855<ref name="Scacchi"/> and has also been found in volcanic deposits on Mount Etna and on Hawai'i.

It is more commonly found in the kainite zones of some marine salt deposits, among them salt mines in Thuringia, Lower Saxony and Saxony-Anhalt (Germany), near Hall in Tirol, Hallstatt and Bad Ischl (Austria), near Whitby (UK), and in the Carlsbad Potash District (New Mexico), also on salt lakes in western China.

Picromerite can also form in sulfate-rich hydrothermal ore deposits and is found in slag heaps of some ore and coal mines.

Picromerite is often accompanied by anhydrite, epsomite, halite, hohmannite, kainite, metasideronatrite and metavoltine, depending on the locality.

== Properties == Picromerite dehydrates in dry air, and crystals then show dull, spherical dehydration zones. Progressive dehydration leads to leonite.

== References == <!--- See http://en.wikipedia.org/wiki/Wikipedia:Footnotes on how to create references using<ref></ref> tags, these references will then appear here automatically --> {{Reflist|refs = <ref name="Mindat">{{cite web | url = http://www.mindat.org/min-3206.html | publisher = Mindat |title = Picromerite}}</ref> <ref name="Scacchi">Arcangelo Scacchi: ''Memoria sullo incendio vesuviano del mese di Maggio''. Nobile, Napoli 1855, p. 191.</ref> <ref name="Datenblatt">''Picromerite'', In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Hrsg.): ''Handbook of Mineralogy, Mineralogical Society of America''. 2001 ([http://www.handbookofmineralogy.org/pdfs/picromerite.pdf PDF 66,3 kB]).</ref> <ref name= "Webmin">{{cite web | url = http://webmineral.com/data/Picromerite.shtml | title = Picromerite | publisher = Webmineral.com}}</ref> }}

== External links == {{commons category|Picromerite}} * {{cite web | url = http://rruff.geo.arizona.edu/AMS/result.php?mineral=Picromerite | publisher = American Mineralogist Crystal Structure Database | title = Picromerite}}

<!--- Categories ---> Category:Potassium minerals Category:Magnesium minerals Category:Sulfate minerals Category:Hexahydrate minerals Category:Monoclinic minerals Category:Minerals in space group 14 Category:Evaporite