University of Colorado

Mineral Structure Data

Melilite Group

The melilite group is composed of minerals of the general formula X2YZ2O7 where X is Ca or Na, Y in Al or Mg and Z is Si or Si + Al. X is a large 8-coordinated site. Y and Z are tetrahedral.

The crystal structure of melilite.


End-Member      Na-Melilite  Gehlenite      Akermanite
Formula         CaNaAlSi2O7    Ca2Al(Al,Si)2O7     Ca2MgSi2O7

Form.Wt. 258.219 274.205 272.640 Z 2 2 2 CrystalSystem Tetr Tetr Tetr PointGroup -42m -42m -42m SpaceGroup P-421m P-421m P-421m UnitCell a(Å) 7.6344 7.7173 7.835 c(Å) 5.0513 5.0860 5.010 Vol(Å3) 294.41 302.91 307.55 MolarVol 88.662 91.220 92.619 Density 2.912 3.006 2.944 Thermal Expansion(Volumetric) alpha 24.0 a0 0.2320 a1 0.2679 Elastic Properties Ks(GPa) G(Gpa)

Mineral Data Base Index

GEOL 1010 Syllabus

GEOL 3010 Syllabus

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