X-RAY-POWDER DIFFRACTION DATA OF HAUYNE WITH INCOMMENSURATE MODULATEDSTRUCTURE FROM VOLCANIC-ROCKS OF LAACHER LAKE, GERMANY

Methods of the structure analysis were used to determine the incommens urate structure modulation in a sample of hauyne from Laacher Lake, Ge rmany. The modulation parameter n = 0.145, determined using single-cry stal patterns, was refined using powder data. An indexing technique fo r additional reflections (satellites) using a parameter subcell and Mi ller index main reflections was suggested. Crystallographic characteri stics of the hauyne of Laacher Lake are compared with that of hauyne f rom Sacrafano (Italy) and with lazurtes from Baikal, Pamir, and Afghan istan. We found that the crystal structure modulation can serve as a s ource of paragenesis information on sulphate bearing sodalte group min erals. (C) 1997 International Centre for Diffraction Data.