Calsilica beads (or Imitation Calsilica) come in basic black & white, as well as brightly-colored, rainbow marbled patterns. Whether it's black & white, or the Rainbow Calsilica variety, it's a synthetic "gemstone" manufactured from a mixture of calcite, plastic/resin 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, most calsilica beads appear to consist of all manmade materials. This is why we refer to our stock as imitation (or faux) calsilica beads. However, they do look great, and they are the same calsilica "stone" that you'll find elsewhere.