The chemical formula of quartz is SiO2
and dark blue to black banded agate
an effect called chatoyancy
with large quartz crystals and bright banded agate in purple and golden yellow
It is harder than variscite and takes a polish
CHM115c Chrysocolla Cabochon Tumbling Materials The chemical formula of quartzThis cabochon is polished out of Chrysocolla rough from Mexico, and shows saturated blue green colors. 36mm x 27mm Designer Cabochons: The Gem Shop, Inc. produces free form designer cabochons for the custom metal smith, hobbyist, and collector. All of the cabs shown are cut and polished by hand in Cedarburg, Wisconsin. The Gem Shop, Inc. specializes in fine agates and fine jaspers including Laguna Agate, Agua Nueva Agate, Natural Druzy, Lace Agate,