Diopside Bertolo S, Nimis P, Dal Negro A American Mineralogist 79 (1994) 668-674 Low-Ca augite from experimental alkali basalt at 18 kbar: Structural variation near the miscibility gap Atomic parameters from ICSD _database_code_amcsd 0001667 9.689 8.824 5.280 90 107.60 90 C2/c atom x y z occ Uiso U(1,1) U(2,2) U(3,3) U(1,2) U(1,3) U(2,3) Ca 0 .2874 .25 .774 .0208 .0325 .0196 0 .0020 0 Na 0 .2874 .25 .226 .0208 .0325 .0196 0 .0020 0 Mg 0 .9056 .25 .901 .0130 .0106 .0162 0 .0036 0 Fe1 0 .9056 .25 .099 .0130 .0106 .0162 0 .0036 0 Si .2917 .0918 .2414 .0133 .0110 .0207 -.0002 .0056 -.0012 O1 .1154 .0868 .1413 .0143 .0170 .0217 .0019 .0049 -.0010 O2 .3679 .2522 .3329 .0269 .0145 .0334 -.0042 .0143 -.0064 O3 .3534 .0174 .0088 .0147 .0368 .0366 -.0008 .0059 -.0191 Fe2 0 .2229 .25 .011 .025