The crystal structure of the mineral sahamalite (Mg,Fe)RE
2(CO
3)
4 (
a=5.894,
b=16.116,
c=4.612 Å;
=106.54°;
Z=2; space group:
P2
1/
a–C
2h
5
) was determined by direct methods and refined with full-matrix least squares for 1453 reflections to
R=0.043. In the atomic arrangement the MO
6 octahedra (M=Mg,Fe) are combined by carbonate groups over common corners to [M(CO
3)
4]
6– chains parallel to [001]. Three of these chains are linked by the RE atoms (resp. REO
9 polyhedra) to a framework.
Die Kristallstruktur des Minerals Sahamalit (Mg,Fe)RE
2(CO
3)
4 (
a=5,894,
b=16,116,
c=4,612 Å;
=106,54°;
Z=2; Raumgruppe:
P2
1/
a–C
2h
5
) wurde anhand direkter Methoden bestimmt. Die Strukturverfeinerung nach der Methode der kleinsten Quadrate (volle Matrix) ergab für 1453 Reflexe
R=0,043. In der Struktur werden MO
6-Oktaeder (M=Mg,Fe) durch Karbonatgruppen über gemeinsame Ecken zu [M(CO
3)
4]
6–-Ketten parallel [100] verknüpft. Je drei dieser Ketten werden über die RE-Atome (bzw. REO
9-Polyeder) zu einem Gerüst verbunden.
Dedicated to Professor Dr.Josef Zemann on the occasion of his 60th birthday.