Pyroxene-ideal Thompson R M, Downs R T American Mineralogist 88 (2003) 653-666 Model pyroxenes I: Ideal pyroxene topologies Pyroxene #8a based on stacking sequence ABABCABC Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience. _database_code_amcsd 0003004 13.063945 6 3.4641016 90 90. 90 P2/c atom x y z SiA 29/32 11/12 1/12 SiB 27/32 5/12 11/12 SiC 13/32 11/12 3/4 SiD 11/32 7/12 1/12 Mg1a 0 5/12 1/4 Mg2a 0 .25 3/4 Mg1b .25 11/12 1/12 Mg2b .25 .25 1/12 Mg1c 1/2 7/12 3/4 Mg2c 1/2 .25 3/4 O1A 13/16 11/12 1/12 O2A 15/16 3/4 11/12 O3A 15/16 1/12 11/12 O1B 15/16 5/12 11/12 O2B 13/16 .25 1/12 O3B 13/16 7/12 1/12 O1C 5/16 11/12 3/4 O2C 7/16 3/4 7/12 O3C 7/16 11/12 1/12 O1D 7/16 7/12 1/12 O2D 5/16 3/4 1/4 O3D 5/16 7/12 3/4