Agate is the banded form of the mineral Chalcedony, which is a microcrystalline variety of Quartz.   There are hundreds of varieties of agate, some which exhibit beautiful colors, banding, and quartz-lined cavities. 

Agate promotes  balance, precision, perception, inner stability, composure, and maturity. Its warm, protective properties encourage security and self-confidence. It is a great crystal to use during pregnancy. [Gienger, 7] Agate also helps new mothers avoid the "baby blues" sometimes experienced after giving birth, and an Agate jewel worn between the breasts encourages lactation.[Megemont, 15]

Agate stops the burning desires for things we do not need, and assists those juggling commitments or multiple jobs. It helps writers express ideas in marketable form, and helps young children learn to walk and not fall as they get older. [Eason, 305] Agate also promotes marital fidelity.[Meloldy, 82]

Agate is useful as a protection amulet when traveling, and is especially effective against traffic accidents. [Megemont, 16]

As a professional support stone, Agate stabilizes the imagination and inspiration of artists, provides personal security for police, telephone workers, cooks, chefs and bakers, and protection from falling objects for builders and construction workers. It provides physical strength and endurance for dancers, dentists, and environmentalists, and emotional endurance for educators and recreational workers. [Mella, 129-133]

Chemical Formula SiO2
Composition Silicon dioxide
Color Multicolored in banded formation. Colors include white, blue, red, green, yellow, orange, brown, pink, purple, gray, and black. Some rarer forms of Agate are iridescent.
Streak White
Hardness 7
Crystal System Hexagonal
Crystal Forms
and Aggregates Agate is a banded microcrystalline form of the mineral Quartz, and does not occur in visible crystals. It occurs in nodules, in massive form, as botryoidal, mammilary, and stalactitic formations, as smooth rounded pebbles, as amygdules, and as the linings of geodes.
Transparency - Translucent to opaque
Tenacity - Brittle
Other ID Marks - 1) Commonly fluorescent, usually green or white. May even show fluorescent banding patterns where some of the bands will fluoresce more strongly than others. 2) Triboluminescent 3) Piezoelectric

Group Silicates -Tectosilicates; Silica Group
Striking Features - Banding patterns
Environment - Agate occurs in all mineral environments, but it is most prevalent in igneous rocks such as basalt.
Rock Type - Igneous, Sedimentary, Metamorphic

Localities found in
The first worked Agate deposits were near Idar-Oberstien, Germany, which has long since been commercially worked out. One of the most abundant sourcs of Agate today is the Rio Grande do Sul in Brazil, where many different sizes and types occur. These Agates are sometimes dyed. Other outstanding South American localities are San Rafael, Mendoza Province, Argentina; and Artigas, Uruguay. Mexico has several famous Agate sources in Chihuahua, the most important being Ojo Laguna, Moctezuma, and Rancho Coyamito. A well-known Agate deposit in Australia is Agate Creek, in Queensland. Poland has some good Agate finds in the Kaczawski Mountains at Nowy Kosciol and Ploczki Gorne.

In the U.S., fine Agate comes from the Dryhead Agate Mine, Carbon Co., Montana; Fairburn, Custer Co., South Dakota; Baker ranch, Luna Co., New Mexico; and from the shores of Lake Superior in the Keweenaw Peninsula of Michigan. "Thunder Egg" Agates are abundant from Jefferson Co., Oregon. The finest iridescent Fire Agate comes from the Black Hills, Graham County, Arizona; and in Mexico in Aguascalientes.

Reference Sources

[Ahsian, pp.] Robert Simmons & Naisha Ahsian, The Book of Stones (Berkley, CA: North Atlantic Books, 2007).

[Eason, pp. ]Cassandra Eason, The New Crystal Bible (London: Carlton Books Ltd., 2010).

[Gienger, pp.] Michael Gienger, Healing Crystals (Scotland: Earthdancer Books, 2009).

[Hall, pp.] Judy Hall, The Crystal Bible (Cincinnati, OH: Walking Stick Press, 2003).

[Hall 2, pp.]Judy Hall, The Crystal Bible 2 (Cincinnati, OH: Walking Stick Press, 2009).

[Megemont, pp.] Florence Megemont, The Metaphysical Book of Gems and Crystals (Rochester, VT: Healing Arts Press, 2008).

[Mella, pp.] Dorothee L. Mella, Stone Power II (Albuquerque, NM: Brotherhood of Life, Inc., 1986).

[Melody, pp.] Melody, Love Is In The Earth (Wheat Ridge, CO: Earth-Love Publishing House, 1995).

[Simmons, pp.] Robert Simmons & Naisha Ahsian, The Book of Stones (Berkley, CA: North Atlantic Books, 2007).