An agate is a beautiful stone of different colors arranged in stripes or bands. Because agates are beautiful to look at, they are often made into jewelery, umbrella handles, paper knives and ornaments. They are also used in some scientific instruments because they are not changed by moisture or fumes.
Agates can be of different shapes and different colors. In ribbon agate the bands of color are almost straight, like striped ribbons; an onyx agate has bands of cloudy color; and in the ring agate or eye agate the bands are in circles. A Mexican agate has one single circle in it like an eye and is called a cyclops agate. (In Greek stories a cyclops was a giant with one eye in the middle of his forehead.) The moss agate has a green coloring in it which looks like moss.
Most agates are found in rocks which first came from volcanoes. Scientists think that when the rocks were cooling down and getting hard after being thrown out of the volcanoes, bubbles of gas collected in them and left holes in the rock. Then, because the rock was not quite hard, water found its way in. There was a substance in the water called silica, which was left behind in the holes when the water drained out. The silica combined with other substances in the rock and gradually layers of different colors became joined together, making the stripes in the agate.
Most agates come from South America, but some are found in North America, Europe, South Africa and Australia. The colors can be changed or made brighter if the stones are soaked in various chemicals.