Description
Agate is a transparent, but sometimes also opaque, variety of quartz and a subvariety of chalcedony. The chemical structure of agate is identical to jasper, flint, and hornstone, and it is often found together with opal. The colorful, striped specimens are used as semi-precious stones. The name agate comes from the Greek Ἀχάτης, Achatès, the name of the present-day Dirillo River in southern Sicily, where agates and other chalcedonies were found. Traditionally, agate was worn as a lucky stone or for healing. Utensils such as buttons were also made from agate. A number of medicinal properties are attributed to agate, such as protection during pregnancy, relief from headaches, skin conditions, and balance disorders. According to various literature, agate is associated with the zodiac signs Aquarius, Taurus, Scorpio, and Gemini. Agate formations occur as a solution of silicic acid in cavities in older rocks. The stones can be artificially stained to obtain color combinations that are more vibrant than those found in nature. The major 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-like quartz crystals, trigonal. Cleavage: none. Color: light blue or gray, but it can also be green. Streak color: none. Luster: vitreous, matte, silky. Hardness (Mohs): 6.5 to 7. Average density: 2.65 kg/dm³. Transparency: transparent to translucent.
