This item is a 16mm amber sphere from the Dominican Republic that I was hoping would demonstrate isotropic behavior.  It doesn't, but is instead a good example of stress-induced anisotropy.  The first photo is of the amber sphere in a polariscope with crossed polarizers.  The interference colors shown are a result of stress-induced anisotropy.  The video shows the behavior of the sphere in a polariscope, first in plane polarized light and then with crossed polarizers.  The last three photos are of the sphere in ambient lighting conditions with a ruler for scale.  There is a bit of crazing on the surface of the amber sphere. 

Thank you, and check out some of our other items for sale.  We aim to provide the nerdiest minerals possible!  Combined shipping available for many items.  Please note, these spheres do act as converging lenses, so best not to leave them in direct sunlight near flammable materials!