thomsonite

{{Infobox mineral | name = Thomsonite | boxwidth = | boxbgcolor =#c7938f | image = Thomsonite-61017.jpg | imagesize = 260px | alt = | caption = | category = Tectosilicate minerals | group = Zeolite group | formula = NaCa2Al5Si5O20·6H2O | IMAsymbol = Thm | molweight = | strunz = 9.GA.10 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | unit cell = | color = colorless, white, beige, and pink | colour = | habit = | twinning = | cleavage = perfect on {010}; good on {100} | fracture = | tenacity = | mohs = 5– | luster = vitreous, pearly | streak = white | diaphaneity = transparent to translucent | gravity = 2.23–2.29 | density = | polish = | opticalprop = | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = | var1 = | var1text = | var2 = | var2text = | var3 = | var3text = | var4 = | var4text = | var5 = | var5text = | var6 = | var6text = }}

Thomsonite is the name of a series of tectosilicate minerals of the zeolite group. Prior to 1997, thomsonite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named thomsonite-Ca and thomsonite-Sr. Thomsonite-Ca, by far the more common of the two, is a hydrous sodium, calcium and aluminium silicate, NaCa2Al5Si5O20·6H2O. Strontium can substitute for the calcium and the appropriate species name depends on the dominant element. The species are visually indistinguishable and the series name thomsonite is used whenever testing has not been performed. Globally, thomsonite is one of the rarer zeolites.