University of Colorado

Mineral Structure Data

Epidote Group

The Epidote group is composed of minerals of the general formula Ca2Al3Si3O12(OH). Zoisite is orthorhombic with Z = 4 whereas clinozoisite and epidote are isostructuiral monoclinic and have Z = 2. Epidote is the name give to the green variety that contains Fe3+ in substitution for AL in one of three octhedral sites. tend to Allanite is a rare earth-rich variety that a trivalent REE in one of the Ca sites and charge compensation is achieved by Fe2+ for Al. Handcockite has Pb and/or Sr substituting in one of the Ca sites.

The crystal structure of epidote .

End-Member      Zoisite     Clinozoisite  Epidote     Handcockite Allanite
Formula         Ca2Al3Si3O12(OH)      Ca2Al3Si3O12(OH)      Ca2FeAl3Si3O12(OH)      Ca(Pb,Sr)FeAl3Si3O12(OH)      CaRE(Fe,Al)3Si3O12(OH)      

Form.Wt. 454.36 454.36 478.6 Z 4 2 2 2 2 CrystalSystem Orth Mono Mono Mono Mono PointGroup mmm 2/m 2/m 2/m 2/m SpaceGroup Pnma P21/m P21/m P21/m P21/m P21/m UnitCell a(Å) 16.212 8.879 8.8877 b(Å) 5.559 5.583 5.6275 c(Å) 10.036 10.155 10.1517 beta 115.50 115.383 Vol(Å3) 904.47 454.36 458.73 MolarVol 136.19 136.83 138.15 Density 3.336 3.321 3.465 Thermal Expansion(Volumetric) alpha a0 a1 a2 Elastic Properties Ks(GPa) G(Gpa)

Mineral Data Base Index

GEOL 1010 Syllabus

GEOL 3010 Syllabus

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