The region of pegmatite dikes in the state of Minas Gerais in Brazil has been the primary source of gem beryl and several other species of colored gemstones for many years. Rivers have cut places through the dikes and alluvial deposits, called "cascalho", which are scattered throughout the region. It is notable that the extensive gemstone deposits in Minas Gerais often yield large aquamarine crystals accompanied by all the other colored varieties of beryl. According to Peter Bancroft in Gem and Crystal Treasures, the principal aquamarine-producing region begins about 75 miles north of Rio de Janeiro and includes the areas of "Conselheiro Pena, Governador Valadares, Teofilo Otoni, Aracuai, Salinas, the Jequitinhonha River basin, and Pedra Azul". Numerous sites lie in the Marambaia Valley in the Teofilo Otoni area alone. Many of the locations have not achieved mine status and may be identified only by the name of a nearby fazenda (plantation). Beautiful gem crystals have been recovered from such unlikely places as water wells, drainage ditches, road cuts, and excavations for building foundations.

Most of the largest and finest aquamarines are from Brazil. Imagine being able to see an object distinctly through the completely transparent length of a 19 by 16 inch hexagonal gemstone prism weighing 520,000 carats! Such a crystal was unearthed by David Mussi in the Papamel mine near Marambaia in 1910. Two Germans purchased the 110 kilogram greenish-blue crystal for 35,000 marks. The gems cut from this gigantic crystal were heat-treated in the first known successful application of this method to remove the undesirable yellow tones and achieve a purer blue color. Jaroslav Bauer and Vladimir Bouska wrote in their book, Precious and Semi-precious Stones, that its yield of 200,000 carats of cut gems supplied the world market with faceted aquamarines for several years.

The standard for comparison of color in aquamarine was set by the smaller 34 kilogram, deep blue Marta Rocha crystal recovered from the same area. This very large crystal was cut into 300,000 carats of magnificent gems. Many crystals of another such rich blue tone have been found in the township of Pedra Azul, formerly known as Fortaleza, and the gems of that hue are called "fortaleza" aquamarines.

The Maxixe mine in the Piaui Valley is the source of the notorious dark blue alkali beryl known as maxixe or maxaxite aquamarine. After its discovery in 1917, several lots of the crystals were sent to Germany for cutting. Peter Bancroft says "there was hell to pay" when its color quickly faded to a "whitish yellow". An investigation disclosed that the color was caused by natural radiation and can be restored, but not permanently, by artificial radiation. The crystals soon became quite popular with collectors as specimens, but they were useless as a gemstones. Dr. Joel Arem states in his Color Encyclopedia of Gemstones that maxixe beryl is "rich in cesium". In The Illustrated Encyclopedia of Minerals and Rocks, Dr. J. Kourimsky attributes the color of maxixe beryl to the presence of boron. Dr. John Sinkankas explains in his book, Emerald and Other Beryls, that it is more probable that the replacement of a missing atom by a vibrating electron in the atomic lattice creates a color center which can be destroyed by light and heat. He cites studies by Nassau and Wood to support this conclusion.

Another atypical deposit of aquamarine is located in the Governador Valadares area of Minas Gerais. This site was mentioned in an earlier "Let's Talk Gemstones" article on beryl. The crystals from that site show a pale green body color obscured by multitudes of exsolved ilminite skeleton inclusions. These inclusions form when iron (hematite) and ilminite in solid solution, having been incorporated into the beryl crystal lattice, become supersaturated, are separated at critical pressures and temperatures, and are later expelled from the crystal lattice. They adapt to the cleavage planes of the growing aquamarine and, by repeated recombination and exsolution, create reddish-brown dendritic patterns. When cut properly en cabochon, a six rayed star emerges from the bronze Schiller effect. Similar material is found in Madagascar. These and other dark star beryls can resemble black star sapphires. Cat's-eye aquamarines are very unusual and are seldom available in the market. Examples are shown in the photographs on page 76 of the Eyewitness handbook, Gemstones, by Cally Hall and on page 48 of the softcover version of Dr. Joel Arem's book, Gems and Jewelry.

Madagascar is the historical source of aquamarine, but is no longer important. A medium dark blue is the color typical of stones that came from that area. Brazil is probably the most prolific supplier of aquamarine today. The natural color of Brazilian gems leans toward bluish-green. Other sources of aquamarine are the African countries of Tanzania, Kenya and Nigeria, the island of Sri Lanka, Afghanistan and Russia. Many huge aquamarine crystals have been found. The largest crystal known was found in Brazil in 1920. It was 19 inches long, 16 inches wide and weighed 243 pounds. It was cut into a number of important gemstones. A 13-pound uncut piece of the green outer portion of the crystal resides in the American Museum of Natural History. The British Museum of Natural History owns an 879.5 carat flawless, step-cut aquamarine with a lovely sea-green color. It is easier to find large gem quality pieces of aquamarine than it is to find such pieces of emerald.