Belonging among general gemstones, agate is a variety of chalcedony, is translucent. Agates are multicolored; common are grey-white, creamy white, bluish-gray, pink, reddish, rarer are green-blue, blue to deep blue, red to red-brown, orange, gray-black, black; they have characteristic mild banding according to which agate is divided into several varieties. Deposits are all over the world, in Asia, the Americas, Australia, Africa and Europe; in the Czech Republic, there are also several sites mainly in the north; probably the most important site was in Germany in Rhineland-Palatinate, that was in 1830 replaced by Brazil (with stones weighing up to hundreds of pounds) after finding local resources of agates.
Its name was given by the Greeks, after discovery of the stone in river Achates in Sicily in 3rd or 4th century BC. Since ancient times people artificially dyed agates, originally by honey that soaked into the pores of the stone, which was then dipped into sulfuric acid – the part of the stone, which contained honey, blackened and residues remained white – result was a variant of agate called onyx; but not agates from all sites can be colored (some are too hard); today is still commonly dyed. Perhaps the most famous monument made of onyx is “Gemma Augustea”, Roman cameo with many figures, led by the emperor Augustus, carved in about 10 to 20 AD; it was purchased by Rudolf II. for 12,000 ducats; now it is on display in Vienna. Usage of agate is documented for ancient Egypt. In the Czech Republic historically agates were used mainly in the Renaissance (family workshop Miseroni) and were used to decorate chapel of St. Wenceslas at St. Vitus cathedral. Amulets of agate are attributed to the general protective function and it is supposed to supply power in tough times. It has excellent hardness and durability, yet avoid scratching by harder materials. It can be cleaned with soap and water followed by rinsing.