This is a natural Aquamarine stone bead, really big faceted marquiz cut at 10x30 mm, made into a pendulum with a simple silver chain. The top bob is a faceted Aquamarine coin shaped bead.
Note: This particular pendulum has iridescent aqua blue glass beads on either side of the marquise Aquamarine instead of the silver ones depicted in the photo. I'll try to take more photos soon....
I always ritually craft my pendulums on a Monday or Wednesday when the Moon is Half Full, and this one is also from a batch that I made on the Libra Moon, June 26, 2023, for even more balance.