Pyroxene-ideal Thompson R M, Downs R T American Mineralogist 88 (2003) 653-666 Model pyroxenes I: Ideal pyroxene topologies Pyroxene #3a based on stacking sequence ABABCACABCBC Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience. _database_code_amcsd 0002998 6.6332495 6 3.4641016 90 100.0250 90 P2/c atom x y z SiA 11/16 7/12 5/16 SiB 13/16 11/12 1/48 Mg1a 0 7/12 3/4 Mg2a 0 .25 3/4 Mg1b 1/2 1/12 3/4 Mg2b 1/2 3/4 3/4 O1A 7/8 7/12 3/8 O2A 5/8 3/4 11/24 O3A 5/8 5/12 11/24 O1B 5/8 1/12 11/24 O2B 7/8 .25 3/8 O3B 7/8 11/12 3/8