Agate gemstones are found in deposits in countries including Brazil, Argentina, Australia, Mexico, India, and Poland. There are also deposits in American in states including Oregon, Arizona, Montana, South Dakota and Michigan. Agate forms within pockets of igneous, sedimentary and metamorphic rocks including melaphyre, porphyry and granite.
Agate gemstones have requisite banding from deposits building over long periods of time. Uniform deposits aren't referred to as agate but are rather classified as carnelian, moss agate or chalcedony. Agate occurs in many colors such as pink, purple, green, red and black. Agate from South America typically occurs in a dull gray color, whereas agate from Germany occurs in vivid pink, red and brown.