Abstract
The variation of unit cell parameters in the wolframite series has been investigated on the specimens synthesized by fusion of various mixtures of FeCl2•4H2O, MnCl2•4H2O and Na2WO4•2H2O. The results show that a0, b0 and c0 increase almost linearly with increasing MnO content as follows: from a0=4.732Å, b0=5.707Å and c0=4.965Å in FeWO4 to a0=4.834Å, b0=5.758Å and c0=4.999Å in MnWO4. Angle β varies also gradually from 90°00′ in FeWO4 to 91°11′ in MnWO4. However, it appears that the value of 90°00′ is maintained in the range from FeWO4 to about (Fe0.9Mn0.1)WO4. The measurement has also been carried out on six natural specimens whose chemical data had been available. The unit cell parameters of these natural wolframites appear to follow the same variation diagram obtained with the synthetic specimens, although some numerical deviations are unavoidable. The differences between the result of chemical analysis and the composition determined by using the variation diagram are within the range of ±6 molper cent.
