paragonite

{{Infobox mineral | name = Paragonite | category = Phyllosilicate minerals | group = Mica group, dioctahedral mica group | boxwidth = | boxbgcolor = | image = ParagoniteWithGarnet 3392.jpg | imagesize = | caption = Paragonite with garnet | formula = | IMAsymbol = Pg | molweight = | strunz = 9.EC.15 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c | color = Colorless, pale yellow, grayish, grayish white, greenish, light apple-green | habit = massive, fibrous or scaly | twinning = common on the [310] less common on the {001} | cleavage = Perfect on the {001} | fracture = Micaeous | tenacity = Elastic | mohs = 2.5–3 | luster = Pearly | polish = | refractive = nα = 1.564 – 1.580 nβ = 1.594 – 1.609 nγ = 1.600 – 1.609 | opticalprop = Biaxial (−) | birefringence = δ = 0.036 | dispersion = r +K+ and apparent micas of intermediate composition is most commonly a microscopic (or even sub-microscopic) intergrowth of two distinct micas, one rich in K, and the other in Na. Paragonite is a common mineral in rocks metamorphosed under blueschist facies conditions along with other sodic minerals such as albite, jadeite and glaucophane. During the transition from blueschist to greenschist facies, paragonite and glaucophane are transformed into chlorite and albite. Jadeite bearing pyroxene minerals have suggested clinozoisite and paragonite are associated and derived from lawsonite releasing quartz and water via the following reaction:

4CaAl2Si2O8(H2O)2 + NaAlSi2O6 2Ca2Al3Si3O12(OH) + NaAl3Si3O10(OH)2 + SiO2 + 6H2O