A green glass bottom with a red garnet top layer produces an emerald-like stone. A diamond is enlarged by cementing it to a crystal base. In doubly-refractive stones, lthe light entering the stone is split into two light rays, and the rays travel in different paths. These stones have more than one refractive index . Calcite, peridot , zircon , tourmaline , and titanite are doubly-refractive stones.
Birefringence is another name for double refraction.
The sharp-edged cut beads are often tumbled and reheated to give them rounded edges. Some examples of drawn beads include seed beads, bugle beads, furnace glass beads, and pony beads. This type of stone makes a nice pendant . Amethyst crystals are often found in a druze. The inner cavity of agate geodes are often lined with a druze of sparkling quartz crystals.