| Abstrakt: |
Data relating to the lattice constants of quartz are reviewed and it is shown that hydrogen and most other impurities increase the a lattice constant and decrease the axial ratio c/a. The available data can be described by c/a=1.10013-0.20 (a-a0) where a0 is the lattice constant of the pure material. The values of a0 at 25° C are deduced to be 4.9127 and 4.9134 Å, respectively, for natural and synthetic quartz with uncertainties in the last figure of about 1. This difference cannot be attributed to the large hydrogen content of the synthetic quartz since it is shown that this has a negligible effect on a. Neither is it due to differences of growth mechanism since crystals of synthetic quartz grown on different faces behave identically. Thus the differences between natural and synthetic quartz must be attributed to differences in the growth conditions (temperature, pressure and mineralizer). This attribution can account for the spread of natural quartz data. |
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