THE CRYSTAL STRUCTURE OF A MICROLITE-GROUP MINERAL WITH A FORMULA NEAR NaCaTa2O6F FROM THE MORRO REDONDO MINE, CORONEL MURTA, MINAS GERAIS, BRAZIL

Author(s)

Andrade, Marcelo B. ^[1] ; Atencio, Daniel ^[2] ; Menezes Filho, Luiz A. D. ^[3] ; Ellena, Javier ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

^[2] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[3] Univ Fed Minas Gerais, Inst Geociencias, BR-31270901 Belo Horizonte, MG - Brazil

• Document type: Journal article
• Source: CANADIAN MINERALOGIST; v. 49, n. 2, p. 615-621, APR 2011.
• Web of Science Citations: 2

Abstract

We present electron-microprobe and single-crystal X-ray-diffraction data for a microlite-group mineral with a formula near NaCaTa(2)O(6)F from the Morro Redondo mine, Coronel Murta, Minas Gerais, Brazil. On the basis of these data, the formula is A(Na(0.88)Ca(0.88)Pb(0.02)square(0.22))(Sigma 2.00) (B)(Ta(1.70)Nb(0.14)Si(0.12)As(0.04))(Sigma 2.00) (X){[}(O(5.75)(OH)(0.25)](Sigma 6.00) (Y)(F(0.73)square(0.27))(Sigma 1.00). According to the new nomenclature for the pyrochlore-supergroup minerals, it is intermediate between fluornatromicrolite and `` fluorcalciomicrolite{''}. The crystal structure, F (d3) over barm, a = 10.4396(12) angstrom, has been refined to an R(1) value of 0.0258 (wR(2) = 0.0715) for 107 reflections (MoK alpha radiation). There is a scarcity of crystal-chemical data for pyrochlore-supergroup minerals in the literature. A compilation of these data is presented here. (AU)

• FAPESP's process: 09/09125-5 - New minerals from Brazil: crystal chemistry characterization and synthesis
• Grantee: Daniel Atencio
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/04984-7 - Determination and refinement of crystal structure of pyrochlore group minerals
• Grantee: Marcelo Barbosa de Andrade
• Support Opportunities: Scholarships in Brazil - Post-Doctoral