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Mineralogical ClassificationAbout crystal-chemical formula of chromdravite
20th Jan 2012 14:26 UTCUwe Kolitsch Manager
The crystal structure of tourmaline with high chromium content (~32 wt % of Cr2O3) from micaceous metasomatites of Onega flexure (a = 16.154, c = 7.427 Å, sp. gr. R3m, R = 0.040, Rw = 0.043) has been refined. The disorder distribution of Cr3+ and Mg2+ cations over Y- and Z-octahedral sites described by the ideal formula Na(Cr2Mg)(Cr4Mg2)(BO3)3(Si6O18)(OH)4 was revealed. The proximity of the common element composition of tourmaline examined to the composition of original chromdravite from the same deposit necessitates the revision of the ideal formula of this mineral species approved before by the commission of IMA.
Page updated.
20th Jan 2012 19:40 UTCMarco E. Ciriotti Manager
20th Jan 2012 23:34 UTCAndrew G. Christy Manager
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: May 14, 2024 20:38:13