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 600C after Cameron et al. (1973)
with O3-O3-O3 angle = 172.9 and model oxygen radius = 1.299
_database_code_amcsd 0003484
9.697 8.980 5.184 90 109.7 90 C2/c
atom     x      y      z
Cr       0  11/12    1/4
Na       0    .25    1/4
Si   .3081   1/12  .2776
O1   .1339   1/12  .1677
O2   .3661    .25  .3323
O3   .3661  .0090  .0552