multi-toned natural Seam Agate dangle earrings. .925 silver. measures about 2-1/2" long, includung ear hooks. Seam agate is a variety of chalcedony that forms within narrow cracks, fractures, or veins of a host rock rather than in rounded, hollow cavities of Silica-rich water seeps into rock cracks—such as basalt in volcanic regions like the Atlas Mountains in Morocco—hardening over long periods.