Dravite Vereshchagin O S, Rozhdestvenskaya I V, Frank-Kamenetskaya O V, Zolotarev A A European Journal of Mineralogy 26 (2014) 309-321 Ion substitutions and structural adjustment in Cr-bearing tourmalines Note: Sample 4 Locality: Umba Valley, Tanzania _database_code_amcsd 0020157 15.921 15.921 7.194 90 90 120 R3m atom x y z occ Uiso CaX 0 0 .2240 .41 .0073 NaX 0 0 .2240 .43 .0073 AlY .12314 .06157 .6370 .67 .0092 CrY .12314 .06157 .6370 .02 .0092 MgY .12314 .06157 .6370 .31 .0092 AlZ .29759 .26131 .61076 .67 .0064 CrZ .29759 .26131 .61076 .02 .0064 MgZ .29759 .26131 .61076 .31 .0064 SiT .19169 .18984 0 .98 .0058 AlT .19169 .18984 0 .02 .0058 B .10964 .21928 .4530 .0069 OHw 0 0 .7710 .89 .0126 O1w 0 0 .7710 .11 .0126 O2 .06032 .12064 .4841 .0120 OHv .2614 .1307 .5106 .89 .0152 O3v .2614 .1307 .5106 .11 .0152 O4 .09305 .18610 .0729 .0113 O5 .1828 .0914 .0937 .0114 O6 .19432 .18431 .7773 .0096 O7 .28534 .28487 .0782 .0096 O8 .20892 .26967 .4394 .0104