Rk. Rastsvetaeva et Ap. Khomyakov, Crystal structure of a new Mn, Na-ordered analogue of eudialyte with the symmetry R3, CRYSTALLO R, 45(4), 2000, pp. 591-594
The crystal structure of a new representative of the eudialyte family was s
tudied. This mineral is characterized by a low calcium content and by order
ing the elements that isomorphically replace calcium, which lowers the symm
etry from R3m to R3. The structure of the sample under study consists of th
e six-membered rings with two octahedra of substantially different volumes,
one occupied mainly by manganese and the other, mainly by sodium and chara
cterized by the average distances of 2.22 and 2.45 Angstrom, respectively.
The formation of such octahedra is the most characteristic structural featu
re of the third low-symmetry mineral of the eudialyte family. (C) 2000 MIAI
K "Nauka/Interperiodica".