The crystal structure of hiortdahlite I

Synthesis and Characterization of Carboxylate−FeOOH Nanoparticles (Ferroxanes) and Ferroxane-Derived Ceramics

“…Thus, Zr is surrounded by 5 Fe; that is, Zr is incorporated within the structure of the ferroxane − AA and is not only adsorbed. The Zr−Fe interatomic distances of 3.3 and 3.6 Å are in the same range as distances found for other Fe−Zr oxides (3.3 Å for the Fe x Zr(Ti) 1 - 0.75 x O 2 - δ ; 3.4 and 3.7 Å for the hiortdahlite; 3.48 Å for the janhaugite).…”

Niocalite and wöhlerite from the alkaline and carbonatite rocks at Kaiserstuhl, Germany

“…The distributions of these cations within the different minerals can be generalised to: cuspidine (Ca)n(Ca)8(Ca)/(Ca)2 niocalite (Ca)n(Ca)8(Ca)z(Nb)2 w0hlerite (Na)4(Ca)8(Zr)2(Nb)2 hiortdahlite (Na,Ca)n(Ca)8(Zr)a(M)2 1Avenite (Na)4(Na,Ca)s(Zr)z(Zr,Ti)z (where M represents a mixing site, in hiortdahlite, with average charge of three, Merlino and Perchiazzi, 1985).…”

“…These minerals have many structural similarities which can only be resolved unambiguously by detailed single crystal X-ray studies. Much of the recent detailed structural work on this group of minerals, particularly by Mellini (1981Mellini ( , 1982 and Merlino and Perchiazzi (1985, 1988, has shown there to be 8 octahedral (or pseudooctahedral) cation sites present. A general formula of these minerals on the basis of 36 oxygens is X16 (Si2OT) Fro.…”

Marianoite, a New Member of the Cuspidine Group From the Prairie Lake Silicocarbonatite, Ontario: Reply

“…The values for the M1 site in wöhlerite and "marianoite", 0.418 and 0.441 Å respectively, compare with the value found for the Nb site in niocalite (0.372 Å). Clearly lower values have been found for the M2 site in wöhlerite and "marianoite", 0.115 and 0.105 Å, respectively, which compare with the values found at other sites presenting a dominant Zr occupancy in minerals of the cuspidine family: the Zr site in låvenite (with some substitution by Nb): d = 0.214 Å (Mellini 1981); the Zr site in hiortdahlite I: d = 0.176 Å (Merlino & Perchiazzi 1985), in hiortdahlite II: d = 0.092 Å (Merlino & Perchiazzi 1987), and in burpalite, d = 0.035 Å (Merlino et al 1990). …”