Zebra Stripes in amethyst
Here is a pic of a diagnostic inclusion for natural amethyst. Often called "zebra stripes" due to it's looking.
In this amethyst specimen, one can see an obvious white mineralization located in one of the layers of the Brazilian law twinning. Making it easy to see even without polarized filters. I tried to show in this picture how the white mineralization looks like and the play of light within the two layers (right and left-handed quartz) of brazillian law twinning.
Picture done with analyser polaroïd, darkfield, and light painting techniques, magnification is about 100X (with camera magnification).