• journal_title：The Canadian Mineralogist
• Contributor：Marcelo B. Andrade ; Daniel Atencio ; Luiz A.D. Menezes Filho ; Javier Ellena
• Publisher：Mineralogical Association of Canada
• Date：2011-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.49.2.615
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：49
• issue：2
• firstpage：615
• section：Articles

d="p-1">We present electron-microprobe and single-crystal X-ray-diffraction data for a microlite-group mineral with a formula near NaCaTa₂O₆F from the Morro Redondo mine, Coronel Murta, Minas Gerais, Brazil. On the basis of these data, the formula is ^A(Na_0.88Ca_0.88Pb_0.02□_0.22)_Σ2.00B(Ta_1.70Nb_0.14Si_0.12As_0.04)_Σ2.00^X[(O_5.75(OH)_0.25]_Σ6.00^Y(F_0.73□_0.27)_Σ1.00. According to the new nomenclature for the pyrochlore-supergroup minerals, it is intermediate between fluornatromicrolite and “fluorcalciomicrolite”. The crystal structure, Fd3̅m, a = 10.4396(12) Å, has been refined to an R₁ value of 0.0258 (wR₂ = 0.0715) for 107 reflections (MoKα radiation). There is a scarcity of crystal-chemical data for pyrochlore-supergroup minerals in the literature. A compilation of these data is presented here.