AM_Melilite
Formula: (Ca1.7 Na.2 K.1) Si2 Mg.5 Al.4 O7
Name: Melilite
Unit cell: 7.789 7.789 5.018 90.0 90.0 90.0 , V=304.43
Space group: P-421M (113)

Smith J V , American Mineralogist , 38 (1953) p.643-661, Reexamination of the crystal structure of melilite