Agates have been cut and made into jewelry for ages. As far back as 4000 B.C. the Samaritans were making necklaces using agates. The name of this stone is said to come from the river Achates, now called Dirille, in the south of Sicily where the historian Pliny said the first agate was discovered.
Agates usually appear to be almost transparent. They are part of the chalcedony family, a microcrystalline variety of quartz. Pure chalcedony is translucent (frosty) gray or white and consists of thin layers of tiny quartz fibers. Banded chalcedony is known as agate. The beauty of agates comes alive when they are cut and polished or tumbled to a beautiful shine.
Moonstone agate is a brilliant, clear stone. Carnelian is bright red and transparent in appearance. Sard is light to dark brown. Ribbon agate is formed from layers of color in strata. Cloud agate is transparent with dark formations running through it. Moss agates are filled with crystallized plant matter. Sometimes they are filled with minerals arranged in dendritic patterns.
Chrysoprase is an apple-green, translucent agate, having a waxy luster. Iris agate (also called rainbow agate) is the only gem that has seven iridescent colors.