agate-information-page

Agate
No gemstone is more creatively striped by nature than agate. This distinct and dramatically banded variety of chalcedony is composed of quartz layers. This composition varies greatly and can be of many colors. The other chalcedony family, jasper, has less-regular patterns and is less defined than the agates. Another difference between the two is that agates tend to be translucent (or at least contain translucent bands), while jaspers are generally opaque. This distinction stems from agate being composed of microscopic "fibers" of crystalline quartz while jasper is made of microscopic "grains" of crystalline quartz. Each individual agate forms by filling a cavity in a host rock. As a result, agate often is found as a round nodule with concentric bands like the rings of a tree trunk. It is said to be named for place in which it first was found — along the River Achates (now called the River Drillo) in Sicily.
In ancient times, agate was highly valued as a talisman or amulet. It was said to quench thirst and protect from fever. Persian magicians used agate to divert storms. Some believe agate renders the wearer invisible, and due to its strength and durability, it is used for making ornaments or for astrological purposes. Being a cooling stone, agate is said to cure insomnia, protect against danger, promote strength and healing, and ensure a healthy life. The major sources of agate are the U.S.A., Australia, Canada and Mexico.

Agate information from Rings & Things website

http://www.rings-things.com/gemstone/index.html