Amazonite from Brazil
|Mohs scale hardness||6-6.5|
|Ultraviolet fluorescence||Weak; olive-green|
Amazonite also known as Amazonstone is a green tectosilicate mineral, a variety of the potassium feldspar called microcline. Its chemical formula is (KAlSi3O8), which is polymorphic to Orthoclase.
Its name is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon area. Although it has been used for 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.
Amazonite is a mineral of limited occurrence. Formerly[when?] it was obtained almost exclusively from the area of Miass in the Ilmensky Mountains, 50 miles southwest of Chelyabinsk, Russia, where it occurs in granitic rocks. Amazonite also occurs in granitic rocks in Jabal Eghei in the Tibesti Mountains, Libya, and in the Baishitouquan granite intrusion in Xinjiang, China. More recently,[when?] high-quality crystals have been obtained from Pike's Peak, Colorado, where it is found associated with smoky quartz, orthoclase, and albite in a coarse granite or pegmatite. Crystals of amazonite can also be found in Crystal Park, El Paso County, Colorado. Other locations in the United States which yield amazonite include the Morefield Mine in Amelia Courthouse, Virginia.
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 small quantities of lead and water in the feldspar.
Crystals of amazonite, from Pikes Peak, El Paso County, Colorado
Large Amazonite crystal from Konso special woreda, Ethiopia. Size: 16.4 x 11.9 x 8.0 cm.
Crystal of amazonite from the Take 5 claim near Florissant, Colorado (size: 4.4 x 4 x 3.5 cm)
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- One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica. 1 (11th ed.). Cambridge University Press. p. 791.
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