Aenigmatite Gasparik T, Parise J B, Reeder R J, Young V G, Wilford W S American Mineralogist 84 (1999) 257-266 Composition, stability, and structure of a new member of the aenigmatite group, Na2Mg4+xFe2-2xSi6+xO20, synthesized at 13-14 GPa _database_code_amcsd 0002100 10.328 10.724 8.805 105.15 96.85 125.47 P-1 atom x y z occ U(1,1) U(2,2) U(3,3) U(1,2) U(1,3) U(2,3) Mg1 0 0 .5 .689 .012 .009 .015 .008 -.003 -.001 Si1 0 0 .5 .060 .012 .009 .015 .008 -.003 -.001 Fe1 0 0 .5 .251 .012 .009 .015 .008 -.003 -.001 Mg2 0 .5 0 .646 .010 .013 .014 .005 .004 .000 Si2 0 .5 0 .056 .010 .013 .014 .005 .004 .000 Fe2 0 .5 0 .298 .010 .013 .014 .005 .004 .000 Mg3 .3139 .8489 .1780 .699 .012 .011 .010 .008 .005 .005 Si3 .3139 .8489 .1780 .061 .012 .011 .010 .008 .005 .005 Fe3 .3139 .8489 .1780 .240 .012 .011 .010 .008 .005 .005 Mg4 .7687 .8191 .1508 .724 .008 .008 .007 .005 .002 .002 Si4 .7687 .8191 .1508 .063 .008 .008 .007 .005 .002 .002 Fe4 .7687 .8191 .1508 .213 .008 .008 .007 .005 .002 .002 Mg5 .0949 .9394 .0559 .765 .009 .015 .013 .007 .006 .007 Si5 .0949 .9394 .0559 .066 .009 .015 .013 .007 .006 .007 Fe5 .0949 .9394 .0559 .169 .009 .015 .013 .007 .006 .007 Mg6 .5959 .9422 .0646 .728 .009 .011 .007 .006 .005 .005 Si6 .5959 .9422 .0646 .063 .009 .011 .007 .006 .005 .005 Fe6 .5959 .9422 .0646 .209 .009 .011 .007 .006 .005 .005 Mg7 .9920 .7350 .2649 .742 .007 .007 .008 .005 .000 .000 Si7 .9920 .7350 .2649 .064 .007 .007 .008 .005 .000 .000 Fe7 .9920 .7350 .2649 .194 .007 .007 .008 .005 .000 .000 Si1 .4767 .2328 .3320 .008 .010 .004 .006 .003 .004 Si2 .9836 .2339 .3451 .009 .011 .008 .007 .004 .006 Si3 .7910 .3428 .2402 .007 .011 .003 .006 .003 .003 Si4 .2793 .3399 .2254 .007 .008 .004 .005 .003 .003 Si5 .6497 .9493 .4436 .008 .006 .008 .004 .003 .004 Si6 .3549 .5602 .0458 .008 .005 .007 .004 .002 .002 Na1 .2093 .6344 .3911 .013 .011 .014 .006 .001 .005 Na2 .6621 .6118 .3698 .011 .014 .020 .008 .006 .010 O1 .3555 .0650 .1628 .007 .009 .010 .005 .006 .007 O2 .8600 .0659 .1743 .007 .011 .016 .007 .004 .007 O3 .5595 .9605 .2915 .006 .012 .008 .005 .000 .004 O4 .0255 .9357 .2693 .024 .030 .010 .020 .000 .003 O5 .2314 .8718 .3902 .010 .004 .006 .006 .002 .001 O6 .7486 .8827 .3901 .010 .005 .011 .005 .003 .004 O7 .4926 .1955 .4984 .007 .013 .009 .006 .005 .005 O8 .9556 .7774 .4830 .011 .014 .017 .005 -.002 .009 O9 .8970 .3218 .3701 .013 .014 .012 .010 .004 .001 O10 .4029 .3363 .3533 .009 .009 .007 .006 .005 .003 O11 .6588 .1729 .0694 .011 .005 .005 .004 .001 -.002 O12 .1538 .1675 .0617 .011 .005 .006 .003 .000 -.002 O13 .5289 .7104 .0353 .013 .006 .007 .006 .004 .001 O14 .0605 .7288 .0654 .006 .011 .025 .007 .001 .004 O15 .2426 .6133 .1125 .008 .010 .007 .007 -.001 .000 O16 .7512 .6099 .1283 .013 .007 .014 .003 .004 -.002 O17 .4034 .5015 .1889 .008 .005 .009 .003 .004 .002 O18 .9347 .5112 .2243 .007 .018 .011 .007 .003 .010 O19 .1664 .3696 .3195 .007 .004 .013 .002 .005 .003 O20 .6738 .3666 .3372 .005 .007 .005 .002 .003 .000