Help mindat.org|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on MindatThe Mindat Store
Minerals by PropertiesMinerals by ChemistryRandom MineralSearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery
bannerbannerbannerbannerbannerbanner

About crystal-chemical formula of chromdravite

Posted by Uwe Kolitsch  
avatar
Uwe Kolitsch January 20, 2012 02:26PM
Rozhdestvenskaya, I. V.; Vereshchagin, O. S.; Frank-Kamenetskaya, O. V.; Zolotarev, A. A.; Pekov, I. V. (2011): About crystal-chemical formula of chromdravite - mineral species from the tourmaline group. Zapiski Rossiiskogo Mineralogicheskogo Obshchestva (Proceedings of the Russian Mineralogical Society) 140, 93-99 (in Russian).

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.



Edited 2 time(s). Last edit at 01/21/2012 04:31PM by Uwe Kolitsch.
avatar
Marco E. Ciriotti January 20, 2012 07:40PM
The correct name of the mineral is chromium-dravite.
avatar
Andrew G. Christy January 20, 2012 11:34PM
An interesting consequence of this disorder is that the distinction between chromium-dravite and hypothetical "chromium-schorl" is lost, since both have Cr3+ as the dominant cation on both types of octahedral site.
Sorry, only registered users may post in this forum.

Click here to login



bannerbannerbannerbannerbannerbanner
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2017, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: July 26, 2017 23:44:50
Go to top of page