Birthstone bracelet October Blue agateDeep Green of October We will introduce a bracelet decorated with birthstones. The birthstones of the parent and top beads stand out among the main beads of crystal. Agate is a general term for a mineral that is made up of small quartz crystals that have gathered together and formed into a mass. It is said that the name comes from the fact that its shape resembles a horse's brain. It is often found in lumps in volcanic rocks, and its characteristic is