Check the listing for details. Snellius Minerals Natural Quartz Sphere. Condition: New. Listed at 5.00 USD. Snellius Minerals Natural Quartz Sphere This item is a natural quartz sphere selected for its ability to display the optical properties of quartz. The natural quartz spheres are fairly uniform and so the photos in this listing are of a representative sphere. Some small variations in size, color, and inclusions do occur, but all can display a quartz uniaxial optic axis interference figure. Sizes run between 10 mm and 15 mm for the quartz spheres in this listing. In contrast to the various natural quartz slices, the quartz sphere allows for many different views through the quartz specimen. However the sphere is a more complicated geometry for thinking about the optical properties of quartz. You will want a polariscope to fully appreciate the natural quartz sphere. The main photo for the listing shows a quartz sphere viewed along the c-crystallographic axis with crossed polarizers displaying a quartz uniaxial optic axis interference figure. The second photo shows a sphere viewed along the c-crystallographic axis with transmitted plane polarized light next to a ruler for scale. The video demonstrates the natural quartz sphere when viewed with crossed polarizers and the hunt for the quartz uniaxial optic axis interference figure.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!