Its name is taken from that of the Amazon River, from which green stones were formerly obtained, though it is unknown whether those stones were amazonite. Although it has been used for[clarification needed] over two thousand years, as attested by archaeological finds in Egypt and Mesopotamia, no ancient or medieval authority mentions it. It was first described as a distinct mineral only in the 18th century.
Green and greenish-blue varieties of potassium feldspars which are predominantly triclinic are designated
as amazonite. It has been described as a "beautiful crystallized variety of a bright verdigris-green" and as possessing a "lively green colour." It is occasionally cut and used as a gemstone.
For many years, the source of amazonite's color was a mystery. Some people assumed the color was due to copper because copper compounds often have blue and green colors. A 1985 study suggest that the blue-green color results from quantities of lead and water in the feldspar. Subsequent 1998 theoretical studies by A. Julg expand on the potential role of aliovalent lead in the color of microcline.
Other studies suggest the colors are associated with the increasing content of lead, rubidium, and thallium ranging in amounts between 0.00X and 0.0X in the feldspars, with even extremely high contents of PbO, lead monoxide, (1% or more) known from the literature. A recent 2010 study also implicated the role of divalent iron in the green coloration. These studies and associated hypotheses indicate the complex nature of the color in amazonite, in other words the aggregate effect of several mutually inclusive and necessary factors.
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^Suayah, Ismail B.; Miller, Jonathan S.; Miller, Brent V.; et al. (April 2006). "Tectonic significance of Late Neoproterozoic granites from the Tibesti massif in southern Libya inferred from Sr and Nd isotopes and U-Pb zircon data". Journal of African Earth Sciences. 44 (4-5): 564. doi:10.1016/j.jafrearsci.2005.11.020. ISSN1464-343X. S2CID26947582.
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^Julg, A. (February 1998). "A theoretical study of the absorption spectra of Pb+ and Pb3+ in site K+ of microcline: application to the color of amazonite". Physics and Chemistry of Minerals. Springer-Verlag. 25 (3): 229-233. doi:10.1007/s002690050108. ISSN1432-2021.