Elasticity of monticellite

Mark S. Peercy, Jay D. Bass

Research output: Contribution to journalArticlepeer-review


The adiabatic single-crystal elastic moduli of a natural sample of monticellite (CaMgSiO4), with the olivine crystal structure, have been measured under ambient conditions using Brillouin spectroscopy. From the single-crystal moduli the aggregate bulk and shear moduli are calculated to be Ks=106±1 and μ = 55.2±0.4 GPa, respectively. These results are consistent with a systematic decrease in bulk modulus with increasing molar volume among the olivine-structured silicates. The longitudinal moduli decrease in the order c11>c33>c22, indicating that the structure is stiffest along the a axis and most compliant along the b axis. This relationship among the longitudinal moduli holds for all silicate and germanate olivines, and is thus inferred to result from the topology of the olivine crystal structure. However, the moduli obtained in this study are at variance with previous conclusions concerning deviations from the Cauchy relations (e.g. c12=c44). For monticellite, off-diagonal shear moduli of the c12-type are uniformly greater than pure shear moduli such as c44. Similar behavior is found in pyroxenes such as diopside. The relative magnitudes of shear and off-diagonal moduli are not, therefore, a diagnostic chemical signature in minerals with complex crystal structures.

Original languageEnglish (US)
Pages (from-to)431-437
Number of pages7
JournalPhysics and Chemistry of Minerals
Issue number5
StatePublished - Dec 1990

ASJC Scopus subject areas

  • General Materials Science
  • Geochemistry and Petrology


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