Crystal-chemical relations classification problems belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite

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Marco E. Ciriotti
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Crystal-chemical relations classification problems belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite

Messaggio da Marco E. Ciriotti » mer 14 dic, 2016 14:51

Prossima pubblicazione.

Referenza:
▪ Bosi, F., Cámara, F., Ciriotti, M.E., Hålenius, U., Reznitskii, L., Stagno, V. (2017): Crystal-chemical relations and classification problems in tourmalines belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite series. European Journal of Mineralogy, 29, (in press)
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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TOSATO FABIO
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Re: Crystal-chemical relations classification problems belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite

Messaggio da TOSATO FABIO » lun 19 dic, 2016 13:51

Complimentissimi a tutti voi.
Tosato Fabio
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Marco E. Ciriotti
Messaggi: 24374
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: Crystal-chemical relations classification problems belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite

Messaggio da Marco E. Ciriotti » mar 10 gen, 2017 19:09

Referenza:
▪ Bosi, F., Cámara, F., Ciriotti, M.E., Hålenius, U., Reznitskii, L., Stagno, V. (2017): Crystal-chemical relations and classification problems in tourmalines belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite series. European Journal of Mineralogy, 29, (in press).

Abstract:
Two oxy-tourmalines showing intermediate compositions between the oxy-schorl and oxy-dravite series (sample from Sludyanka crystalline complex, Baikal, Russia) and the oxy-dravite and bosiite series (sample from the Valletta mine, Piedmont, Italy) were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis, optical absorption and Synchrotron Mössbauer source spectroscopy. A comparative analysis of the results, along with data from literature on additional samples corresponding to the species oxy-schorl, oxy-dravite, bosiite and povondraite, show that the main structural variations within the Fe-bearing, Na-dominant oxy-tourmalines are related to variations in the content of Fe, which is incorporated into the structure via substitution mechanisms that involves Al. The results also show the occurrence of a complete substitution series from oxy-schorl via oxy-dravite and bosiite to povondraite, but no (or a limited) direct substitution series between oxy-schorl and bosiite (or povondraite). The substitution of Al by larger cations causes changes in ⟨Y–O⟩ and ⟨Z–O⟩ distances as well as in the unit-cell parameters. The effect of ⟨Y–O⟩ on the a-parameter is evident in the oxy-schorl–oxy-dravite series, but it is of marginal significance in the oxy-dravite–bosiite–povondraite series. On the other hand, a good correlation exists between ⟨Z–O⟩ and the a-parameter only in the oxy-dravite–bosiite–povondraite series. The c-parameter is strongly correlated with ⟨Z–O⟩ along the entire substitution series.
Classification problems related to the naming of Fe-bearing, Na-dominant oxy-tourmalines are discussed. Application of the nomenclature rules in force resulted in ambiguous naming of the studied samples. This makes, for example, direct comparisons of physical and chemical properties of tourmalines originating from different deposits difficult.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 24374
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Crystal-chemical relations classification problems belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite

Messaggio da Marco E. Ciriotti » ven 30 giu, 2017 18:17

Pubblicazione effettuata.

Referenza:
▪ Bosi, F., Cámara, F., Ciriotti, M.E., Hålenius, U., Reznitskii, L., Stagno, V. (2017): Crystal-chemical relations and classification problems in tourmalines belonging to the oxy-schorl – oxy-dravite – bosiite – povondraite series. European Journal of Mineralogy, 29, 445-455.

Abstract:
Two oxy-tourmalines showing intermediate compositions between the oxy-schorl and oxy-dravite series (sample from Sludyanka crystalline complex, Baikal, Russia) and the oxy-dravite and bosiite series (sample from the Valletta mine, Piedmont, Italy) were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis, optical absorption and Synchrotron Mössbauer source spectroscopy. A comparative analysis of the results, along with data from literature on additional samples corresponding to the species oxy-schorl, oxy-dravite, bosiite and povondraite, show that the main structural variations within the Fe-bearing, Na-dominant oxy-tourmalines are related to variations in the content of Fe, which is incorporated into the structure via substitution mechanisms that involves Al. The results also show the occurrence of a complete substitution series from oxy-schorl via oxy-dravite and bosiite to povondraite, but no (or a limited) direct substitution series between oxy-schorl and bosiite (or povondraite). The substitution of Al by larger cations causes changes in ⟨Y–O⟩ and ⟨Z–O⟩ distances as well as in the unit-cell parameters. The effect of ⟨Y–O⟩ on the a-parameter is evident in the oxy-schorl–oxy-dravite series, but it is of marginal significance in the oxy-dravite–bosiite–povondraite series. On the other hand, a good correlation exists between ⟨Z–O⟩ and the a-parameter only in the oxy-dravite–bosiite–povondraite series. The c-parameter is strongly correlated with ⟨Z–O⟩ along the entire substitution series.
Classification problems related to the naming of Fe-bearing, Na-dominant oxy-tourmalines are discussed. Application of the nomenclature rules in force resulted in ambiguous naming of the studied samples. This makes, for example, direct comparisons of physical and chemical properties of tourmalines originating from different deposits difficult.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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