Eastonite

Mica Group. Compare the chemically similar phlogopite. Forms a series with siderophyllite. Trioctahedral mica.

Structural context

Eastonite
Crystal System monoclinicCrystal Class sphenoidalSpace Group C2
a5.3
b5.3
c7.2—10.2 (8.7)
alpha90
beta90.5—100.6 (95.55)
gamma90
volume202.24—281.629 (241.9345)

Based on 2 measurements

Chemical context

Stoichiometric formulas

Eastonite
mindat.org
  • March 13, 2023KMg2Al(Al2Si2O10)(OH)2
IMA
  • March 13, 2023KAlMg2(Si2Al2)O10(OH)2
mineralogy.rocks
  • Aug. 30, 2022KAlMg2(Si2Al2)O10(OH)2