Imitation rainbow calsilica beads come in brightly-colored, marbled patterns! Choose from various bead shapes to add color and visual interest to your jewelry creations. Rainbow Calsilica is a synthetic "gemstone" manufactured from a mixture of calcite, plastic and artificial coloring pigments. Although some claim that calsilica is a naturally occurring material, there is little evidence to support this claim (the most persistent claim is that calsilica is mined in Chihuahua, Mexico). While some rainbow calsilica beads consist of powdered carbonate rock that is artificially colored and stabilized with plastic, our calsilica beads most likely consist of all manmade materials. This is why we refer to our stock as imitation (or faux) calsilica beads.