Pyroxene-ideal
Thompson R M, Downs R T
American Mineralogist 89 (2004) 614-628
Model pyroxenes II: Structural variation as a function of tetrahedral rotation
model kosmochlor at 9.28 GPa after Origlieri et al. (2003)
with O3-O3-O3 angle = 166.1 and model oxygen radius = 1.271
_database_code_amcsd 0003486
9.401 8.738 5.045 90 108.7 90 C2/c
atom     x      y      z
Cr       0  11/12    1/4
Na       0    .25    1/4
Si   .3082   1/12  .2672
O1   .1335   1/12  .1630
O2   .3665    .25  .3370
O3   .3665  .0180  .0343