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 after Cameron et al. (1973)
with O3-O3-O3 angle = 172.0 and model oxygen radius = 1.294
_database_code_amcsd 0003483
9.653 8.944 5.164 90 109.6 90 C2/c
atom     x      y      z
Cr       0  11/12    1/4
Na       0    .25    1/4
Si   .3081   1/12  .2763
O1   .1338   1/12  .1672
O2   .3662    .25  .3328
O3   .3662  .0100  .0527