pollucite

{{Short description|Zeolite mineral}}

{{Infobox mineral

| name = Pollucite

| category = Tectosilicate minerals, zeolite group

| boxwidth =

| boxbgcolor =

| image = Pollucite-193819.jpg

| imagesize = 260px

| caption = Euhedral, tabular crystal of colorless, translucent and lustrous pollucite with frosted crystal faces from Afghanistan (size: 2.7 x 2.4 x 1.2 cm)

| formula = {{chem2|Cs(Si2Al)O6*nH2O}}

| IMAsymbol = Pol{{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}}

| strunz = 9.GB.05

| dana = 77.1.1.2

| system = Isometric

| class = Hexoctahedral (m{{overline|3}}m)
H-M symbol: (4/m {{overline|3}} 2/m)

| symmetry = Ia{{overline|3}}d

| unit cell = a = 13.67 Å; Z = 16

| color = Usually colorless; also white, grey, pink, blue or violet

| habit = Usually massive; rare crystals are normally trapezohedral or cubic

| twinning =

| cleavage = None observed

| fracture = Conchoidal to uneven

| tenacity = Brittle

| mohs = 6.5 to 7

| luster = Vitreous to greasy

| refractive = 1.508–1.528

| opticalprop = Isotropic or very weakly anisotropic

| birefringence =

| pleochroism =

| streak = White

| gravity = 2.7 to 3.0

| density =

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| fusibility =

| diagnostic =

| solubility = Readily soluble in HF; dissolves with difficulty in hot HCl

| diaphaneity = Transparent to translucent

| other = Sometimes weakly fluorescent under SW and LW UV

| references = [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Pollucite Mineralienatlas]Gaines, et al. (1997) Dana's New Mineralogy, Wiley {{ISBN|978-0471193104}}[http://www.mindat.org/min-3255.html Pollucite on Mindat.org][http://webmineral.com/data/Pollucite.shtml Pollucite data on Webmineral][http://rruff.geo.arizona.edu/doclib/hom/pollucite.pdf Handbook of Mineralogy]}}

Pollucite is a zeolite mineral with the formula {{chem2|(Cs,Na)2Al2Si4O12*2H2O}} with iron, calcium, rubidium and potassium as common substituting elements. It is important as a significant ore of caesium and sometimes rubidium. It forms a solid solution series with analcime. It crystallizes in the isometric-hexoctahedral crystal system as colorless, white, gray, or rarely pink and blue masses. Well-formed crystals are rare. It has a Mohs hardness of 6.5 and a specific gravity of 2.9, with a brittle fracture and no cleavage.