Optical Calcite Sphere

Optical calcite sphere with rainbows and layers facing every direction. Each measures 40-42 mm in diametere and are approximately 100 grams. For transparency: These were sold to me as gypsum selenite spheres, but they are harder than typical gypsum (2). A box knife, peridot (6.5-7), lapis lazuli (5-6), apatite (5), and caribbean calcite (3-3.5) scratch the sphere but malachite (3.5-4), fluorite (4) and bladed barite (3-3.5) do not scratch.