A hexagonal crystal formation that generally occurs in rock cavities with silica-rich surroundings, such as volcanic rocks and limestone beds, agate can also form inside coral. Agate comes in a wide range of colors depending on trace mineral components and in numerous configurations, some featuring lace-like surface designs or layered stripes, others formed as pure rock crystal. Considered one of the seven precious stones in Buddhism (shippō), agate beads decorate religious implements and decorative art objects that were presented as donations to Tōdaiji. See also Shippō.