piypite

{{Short description|Rare potassium, copper sulfate mineral}}

{{infobox mineral

| name = Piypite

| image = Piypite-88672.jpg

| alt =

| caption = Green acicular crystals of piypite

| category = Sulfate mineral

| formula = K₂Cu₂O(SO₄)₂

| IMAsymbol = Piy{{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}}

| molweight =

| strunz = 7.BC.40

| dana =

| system = Tetragonal

| class = Pyramidal (4)
H-M symbol: (4)

| symmetry = I4

| unit cell = a = 13.6 Å, c = 4.95 Å; Z = 2

| color = Emerald-green, dark green, black

| colour =

| habit = Acicular crystals elongated along [001], square cross section, commonly hollow; also as mosslike aggregates

| twinning =

| cleavage = Perfect, parallel to elongation

| fracture =

| tenacity = Brittle

| mohs = 2.5

| luster = Vitreous to greasy

| streak = Yellowish green

| diaphaneity = Transparent to translucent

| gravity = 3.0 - 3.1

| density =

| polish =

| opticalprop = Uniaxial (+)

| refractive = n_ω = 1.583 n_ε = 1.695

| birefringence = δ = 0.112

| pleochroism = Distinct; O = pale green, yellowish green; E = deep green, pale yellowish green

| 2V =

| dispersion =

| extinction =

| length fast/slow =

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| melt =

| fusibility =

| diagnostic =

| solubility = Soluble in water, leaves residue

| impurities =

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| other =

| references = [http://www.mindat.org/min-3225.html Piypite on Mindat.org][http://rruff.info/doclib/hom/piypite.pdf Piypite in the Handbook ov Mineralogy][http://webmineral.com/data/Piypite.shtml#.Uu-cnz3MRVY Piypite data on Webmineral][https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Piypite Mineralienatlas]

}}

Piypite is a rare potassium, copper sulfate mineral with formula: K₂Cu₂O(SO₄)₂. It crystallizes in the tetragonal system and occurs as needlelike crystals and masses. Individual crystals are square in cross-section and often hollow. It is emerald green to black in color with a vitreous to greasy luster.

It was first described in 1982 for an occurrence in the Main Fracture of the Tolbachik volcano, Kamchatka Oblast, Russia. It has also been reported from Mount Vesuvius, Italy, and in a slag deposit in the Bad Ems District in the Rhineland-Palatinate, Germany. Piypite occurs as a sublimate phase in a fumarole environment. Associated minerals include halite, sylvite, langbeinite, tenorite, hematite, tolbachite, dolerophanite, urusovite, aphthitalite, ponomarevite, cotunnite, chalcocyanite, sofiite, euchlorine, averievite, fedotovite, alarsite, alumoklyuchevskite, nabokoite and lammerite at the type locality in Kamchatka. On Vesuvius, it occurs with paratacamite.