Agate is the name given to numerous varieties of banded chalcedony, a mineral of the quartz family. A generally accepted requirement in the definition of agate is that it has to be banded. This qualification distinguishes it from other forms of chalcedony which are not banded. Exceptions include dendritic agate and moss agate, which are not true agates since they lack the banding patterns, but they are still traditionally called agates since they have more than one color. Onyx, when banded white and black, is technically a form of agate, and sardonyx, which is a banded reddish and white chalcedony, is also technically a type of agate.
Agate’s name comes from the Achates River in Sicily, where agates were first found. Usually banded in layers, or stripes, some varieties have "eye" markings or specks of color, some have fossilized inclusions, and others are solid. The layered bands of microscopic quartz in agate may appear delicate, they are actually very strong. There are hundreds, if not thousands of types of agates. Called the earth rainbow, the concentric bands of agate form in nearly every color the earth can produce, including a colorless form.
Agates are found all around the world. Historically, agates have been discovered with the artifacts of Neolithic people and were used as healing amulets and ornamentation dating back to Babylon. Its medicinal uses continued through the ancient Greek and Egyptian civilizations and spread throughout Africa and the Middle East into Russia. Agate sparked a world-renowned stonecutting and polishing industry in Germany, in the Idar-Oberstein region, that flourished from the 15th to the 19th century, and exists today.
Metaphysically, agate has a lower intensity and vibrates to a slower frequency than other stones, but is highly regarded as a stabilizing and strengthening influence. Agate is excellent for balancing emotional, physical, and intellectual energy, and in harmonizing yin and yang, the positive and negative forces of the universe.
Throughout history and all cultures, moss agate has been known as the crystal of gardeners and agriculture and contains dense inclusions of green hornblende that cause the pattern to resemble moss. The field is clear or milky white quartz. The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron. Moss agate is a semi-precious gemstone technically not a true agate, agate's defining feature of concentric banding. Despite its name, moss agate does not contain organic matter and is usually formed from weathered volcanic rocks.
It was considered a miraculous healing stone for tribal priests of the past, giving them the power to interact with our human organic system, and was used as a talisman to make warriors strong and victorious.
Montana moss agate is found in the alluvial gravels of the Yellowstone River and its tributaries between Sidney and Billings, Montana. It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity. In Montana moss agate the red color is the result of iron oxide and the black color is the result of manganese oxide.
Dendritic agate is a whitish-gray or colorless chalcedony with a tree or fern-like markings known as dendrites. The varietal name agate is used for this gem even though it does not exhibit the banding that is typical of agate. The dendrites in dendritic agate are iron or manganese inclusions and are usually brown or black in color. Though they appear organic due to their fern-like structure, they are actually inorganic.
The famous Russian jeweler Carl Faberge used dendritic agate along with diamond and other precious stones for many of his pieces. Dendritic agate is prized in Russia as a stone of longevity, good health, and prosperity. It is also believed that it improves self-esteem and emotional balance.
Dendritic agate deposits are found in Brazil, India, Madagascar, the USA, Mexico, and Kazakhstan.