Gleaming Big Pine Green Bamboo Sardonyx Agate Tube BeadsPrice is for 14 inches of these natural green agate beads. Each bead measures 17mm x 12mm and about 20 beads in a string . Agate is one of the most common bead beaders use because it is readily available in an abundance of styles and shapes. What is agate? Agate is a variety of microcrystalline quartz that forms in layers and many colours and texture, by filling a cavity in a host rock although it is usually in round nodules with bands looking like