Beefy Forest-Green Agate Barrel Beads - Heavy 15mm!Price is per 15 inch string of these beautiful beads. Each measures 15mm x 13mm. Heavy! What is agate? Agate is nature's most striped gemstone. 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 eyes in the rings of a tree trunk. Different colours are caused by iron oxide or limonite crystals carried by water seeping