Agate occurs in modular masses in rocks such as volcanic lavas. When split open, they reveal an amazing variety of colors and patterns. Band colors are defined by differing impurities present. No gemstone is more creatively striped by Nature than agate, chalcedony quartz that forms in concentric layers in a wide variety of colours and textures. Each individual agate forms by filling a cavity in host rock. As a result, agate is often found as a round nodule, with concentric bands like
the rings of a tree trunk. The bands sometimes look like eyes, fanciful scallops, or even a landscape with trees. Agate is oftenly dyed to enhance the natural color. Agate also occurs in several distinct forms. agate is usually cut as thin slabs or polished as ornaments. Agatized wood is fossilized wood that has had its organic matter replaced by agate. The most famous agates are mined from Idar-Oberstein in Germany, where agate has been collected since 1548. The mining of agate in the Nahe River valley in Germany, which was already documented in 1497, gave rise to the cutting-centre of Idar-Oberstein.
Originally, the river was used to power the grinding-wheels. When the Nahe agate deposit had been exhausted, in the nineteenth century. Agate was highly valued as a talisman or amulet in ancient times. It was said to quench thirst and protect against fever. Persian magicians used agate to divert storms. A famous collection of two to four thousand agate bowls which was accumulated by Mithridates, king of Pontus, shows the enthusiasm with which agate was regarded. Agate bowls were also popular in the Byzantine Empire. Collecting agate bowls became common among European royalty during the Renaissance and many museums in Europe, including the Louvre, have spectacular examples.
