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The movie clip to the left shows a fragment of alpha quartz
displacively transforming to beta quartz as it is heated to the
temperature of 573.1 deg. C. The displacive transformation is marked by
a sweeping change in interference color. In cross-polarized
light, the fragment of alpha quartz appears purplish, but rapidly changes
to pinkish-orange as the "front" of beta quartz sweeps from right to left.
Note the opposite occurs upon cooling through 573.1 deg.C.
The change in interference color is subtle, but notable.
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