Agate is a cryptocrystalline variety of silica, chiefly chalcedony, characterized by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.
Conch is a common name that is applied to a number of different medium to large-sized sea snails or their shells. The term generally applies to large snails whose shell has a high spire and a noticeable siphonal canal (in other words, the shell comes to a noticeable point at both ends). Conch jewelry is set with queen conch shells that are precisely cut and polished to the desired design.