Figure 9-11. Comparison of powder data of unknown with possible unit-cell data. 



minerals, the mixture appeared to be a single homogeneous substance. A 

 diffraction-powder pattern, however, definitely showed it to be a mixture. With 

 the regular powder methods described above, one constituent could readily be 

 identified as quartz from these powder data. This identification is further 

 verified by direct comparison with a standard quartz pattern (fig. 9-10). 



Assuming that powder data were not available for the other constituent of 

 the mixture, it would then be impossible to identify this constituent with the aid 

 of the card index. However, if now through more thorough optical examination, 

 further data can be obtained to limit the number of possible compounds to be 

 checked to a reasonable number, identification will still be possible if suitable 

 unit-cell data are available. In this case, this would involve careful checking of 



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