RALSTONITE RENAMED HYDROKENORALSTONITE, COULSELLITE RENAMED FLUORNATROCOULSELLITE, AND THEIR INCORPORATION INTO THE PYROCHLORE SUPERGROUP

摘要

Ralstonite is renamed hydrokenoralstonite, ideally square 2Al2F6(H2O). "Atroarite" and the "AHF" phase (hydrated aluminum hydroxy-fluoride, a "ralstonite-like mineral") are also hydrokenoralstonite. The name ralstonite is transferred to the group, where M3+ cations are dominant at the B site, and Al is dominant among them, and F1- is the dominant anion at the X site. Hydrokenoralstonite from the Pitinga mine, Presidente Figueiredo, Amazonas, Brazil, is intimately associated with galena and sphalerite. It forms chemically homogeneous octahedral crystals, from 0.1 to 1 mm in size. The mineral is colorless with white streak, vitreous luster, transparent, density (calc.): 2.554 g/cm(3). Its empirical formula is (square 1.87Na0.12Rb0.01)(Sigma 2.00) (Al1.86Mg0.14)(Sigma 2.00)[F-3.46(OH)(2.54)](Sigma 6.00)(H2O). The mineral is cubic, Fd (3) over barm (#227), a 9.8455(7) (A) over circle , V 954.36 (12) (A) over circle (3), Z = 8. Hydrokenoralstonite exhibits ( Al, Mg) cations with octahedral coordination and Na cations located within distorted cubes. Coulsellite, a rhombohedral pyrochlore-supergroup mineral, ideally (Na,Ca)(2)(Mg,Al)(2)F6F, is renamed fluornatrocoulsellite, and the name coulsellite is transferred to the group, where M2+ cations are dominant at the B site, and Mg is dominant among them, and F1- is the dominant anion at the X site. This nomenclature proposal was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association.