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Mineralogical ClassificationIMA 2006-020 = alloriite

12th Oct 2006 21:16 UTCMarco E. Ciriotti Manager

From Excalibur catalogue:


ALLORIITE- Monte Cavallucio, Campagnano, Lazio Italy


This NEW SPECIES forms minute colorless to pale violet tabular to stout prismatic micro hexagonal crystals in vugs, typically associated with sanidine, andradite, "biotite" etc. IMA#2006-020, and named for well known amateur mineralogist and collector Roberto Allori (b. 1933) who found the mineral. Formula: (Na,Ca,K)26
(SO4)6Cl2, a new member of the cancrinite group and analog of afghanite. (omissis).



Complimenti vivissimi al grande AMIco Roberto!

14th Oct 2006 14:47 UTCMarco E. Ciriotti Manager

The best crystals are not so minute!

The formula expressed by Excalibur is quite different from this listed in the CNMNC IMA "Proposal approved in August 2006": Na5K1.5Ca(Si6Al6O24)(SO4)(OH)0.5·H2O

15th Oct 2006 19:59 UTCJim Ferraiolo

The Excalibur formula was probably supplied by the author.

15th Oct 2006 20:31 UTCMarco E. Ciriotti Manager

Yes, Jim, I think that it is more correct.

16th Oct 2006 00:54 UTCAntonio Borrelli Expert

Is the Excalibur formula the best to characterize alloriite?

16th Oct 2006 01:12 UTCJim Ferraiolo

As far as we can tell,yes. This is assuming that the new composition was supplied by the author.

18th Oct 2006 16:48 UTCPeter Haas

The "Excalibur formula" also matches up better with the cancrinite group, to which alloriite belongs. Slightly rewritten, it reads: (Na,Ca,K)26Ca4
. Note, that the cancrinite group members are composed of a (Al6Si6O24)n polyanion, so we can assume a Si:Al atomic ratio of 1:1 (as also indicated in the CNMNC formula). If we multiply the CNMNC formula by 4 (basically, this is just a matter of how Z is defined), we obtain Na20K6Ca4(Al6Si6O24)4(SO4)4(OH)2·2H2O, or (Na,K)26Ca4<(OH)2|(SO4)4|(Al6Si6O24)4>.2H2O. This is strikingly similar to the Excalibur formula, at least for the cations.

18th Oct 2006 17:00 UTCPeter Haas

Data added. I used the formula with chloride ions. Whether there are chloride (Excalibur) or hydroxide (CNMNC) anions present will hopefully be solved in the paper to come.

11th Jan 2007 11:36 UTCMarco E. Ciriotti Manager

Thanks to Roberto Allori I was informed that the type-description of the new mineral alloriite is now published. Here is the reference.


Reference:

• Chukanov, N.V., Rastsvetaeva, R.K., Pekov, I.V., Zadov, A.E. (2007): Alloriite, Na5K1.5Ca(Si6Al6O24)(SO4)(OH)0.5·H2O, a new mineral of the cancrinite group. Zapiski Vserossiskogo Mineralogicheskogo Obshchetstva, 137(1), 86-93.
 
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