Agate is a variety of quartz (silica) characterized by its fineness of grain and brightness of color. Although agates can be found in many different types of rock, they are usually associated with volcanic rock.
Theophrastus, a Greek philosopher and naturalist, discovered this stone along the River Achates in the 3rd century BC. It had widespread use in the ancient world as a material used in the art of hardstone carving, and has been found at a number of ancient sites.
Agates develop as deposits in hollow cavities, called vesicles. While they can form in all types of rock, most agates developed in ancient volcanic lava.
There are thousands of named agates found in almost all countries of the world. Some are named by their formation type, such as 'fortification' agate. Others are named for the location in which they were found, such as Brazilian Agate. Sometimes, the name is derived from a combination of the two types, such as a Brazilian Fortification Agate.
A friend of mine recently moved to Castle Rock, Washington, a small town near the base of Mount St. Helens. While he was building a new home on a large parcel of land, he picked up handfuls of gravel with small visible veins of agate in them. He put them in a rock polisher for several weeks to see what would be left after the grit and sand removed the soft outer layer of the rocks. The result was a beautiful collection of some of the nicest agates I have seen.
I have been a rock collector since I was a small child, with a little help from my grandfather Ernest and his brother Benton. They spent years in Oregon collecting agates and thundereggs, and had a rock shop where they could polish and cut slabs of geodes and petrified wood and agates. These beautiful agates will be a wonderful addition to my own rock collection.
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