Agate “spheres” tumbled, sometimes even with water in them (“water agates”).

Agate is a transparent, but sometimes also opaque, variety of quartz and a sub-variety of chalcedony. The chemical structure of agate is identical to that of jasper, flint and chert and is often found together with opal. The colourful, striped specimens are used as semi-precious stones. The name agate comes from the Greek Ἀχάτης, Achatès, the name of the current river Dirillo in the south of Sicily, where agates and other chalcedony were found. Traditionally, agate was worn as a lucky stone or for healing. Agate was also used to make consumer goods, such as buttons. A number of medicinal properties are attributed to agate, such as protection during pregnancy and against headaches, skin conditions and balance disorders. According to various literature, agate belongs to the zodiac signs Aquarius, Taurus, Scorpio and Gemini. Agate compounds form as a solution of silicic acid in cavities in older rocks. The stones can be artificially stained to obtain colour combinations that are more vibrant than those found in nature. The main sources of agate are Brazil, Uruguay and the United States (Oregon, Washington and around Lake Superior). Closer to the Netherlands and Belgium, agate is also found in the Hunsrück in Germany. Chemical composition: SiO₂ + Al, Ca, Fe, Mn Crystal system: belongs to chalcedony quartz crystals, trigona Cleavage: none. Color: light blue or gray, but it can also be green Streak color: none Gloss: glass gloss, matte, semi-gloss Hardness (Mohs): 6.5 to 7. Average density: 2.65 kg/d Transparency: transparent to translucent