Pyroxene-ideal Thompson R M, Downs R T American Mineralogist 88 (2003) 653-666 Model pyroxenes I: Ideal pyroxene topologies Pyroxene #4 based on CCP stacking sequence ABCABCABCABC. Ideal analogue of HP-C2/c pyroxene and eight-coordinaSiEd Mg2-C2/c pyroxene. Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience. _database_code_amcsd 0003000 6.6332495 6.0 3.4641016 90 100.0250 90 C2/c atom x y z Si 5/16 1/12 3/16 Mg1 0 11/12 1/4 Mg2 0 .25 1/4 O1 1/8 1/12 1/8 O2 3/8 .25 3/8 O3 3/8 1/12 7/8