Amazonite

Amazonite
Photo of a turquoise mineral with beige microcline speckled within it
Amazonite from Brazil
General
CategoryTectosilicate
Formula
(repeating unit)		KAlSi3O8
Crystal systemTriclinic
Identification
ColorGreen, blue-green
Crystal habitPrismatic
CleavagePerfect
FractureUneven, splintery
TenacityBrittle
Mohs scale hardness6.0–6.5
LusterVitreous
StreakWhite
DiaphaneityTranslucent, opaque
Specific gravity2.56–2.58
Refractive index1.522–1.530
Birefringence−0.008
PleochroismAbsent
DispersionNone
Ultraviolet fluorescenceWeak; olive-green
Other characteristics Radioactive 14.05% (K)
References[1][2][3]:214–215

Amazonite, also known as amazonstone,[4] is a green tectosilicate mineral, a variety of the potassium feldspar called microcline.[4][5][6] Its chemical formula is KAlSi3O8,[1][7] which is polymorphic to orthoclase.

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.[4] Although it has been used for jewellery for well over three thousand years, as attested by archaeological finds in Middle and New Kingdom Egypt[8] and Mesopotamia, no ancient or medieval authority mentions it. It was first described as a distinct mineral only in the 18th century.[9]

Green and greenish-blue varieties of potassium feldspars that are predominantly triclinic are designated as amazonite.[10] It has been described as a "beautiful crystallized variety of a bright verdigris-green"[11] and as possessing a "lively green colour".[4] It is occasionally cut and used as a gemstone.[12]

  1. ^ a b Walter, Schumann (1997). Gemstones of the world (Rev. & expanded ed.). New York: Sterling Pub. Co. p. 164. ISBN 0806994614 – via Internet Archive.
  2. ^ "Radioactive Gems : ClassicGems.net". ClassicGems.net. Archived from the original on 2021-02-11. Retrieved 2021-08-13.
  3. ^ Schlegel, Dorothy McKenney (1957). "Gem Stones of the United States". Geological Survey Bulletin (1042-G). United States Government Publishing Office – via Google Books.
  4. ^ a b c d  One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Amazon-stone". Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. p. 791.
  5. ^ "Amazonite gemstone information". gemdat.org. Archived from the original on 2021-03-01. Retrieved 2018-08-24.
  6. ^ "Amazonite".
  7. ^ "Amazonite: Amazonite mineral information and data". mindat.org. Archived from the original on 14 May 2021. Retrieved 13 April 2017.
  8. ^ Harrell and Osman 2007
  9. ^ Mikhail Ostrooumov, Amazonite: Mineralogy, Crystal Chemistry, and Typomorphism (Elsevier, 2016), p. 1–12.
  10. ^ Pivec, E.; Ševčik, J.; Ulrych, J. (December 1981). "Amazonite from the alkali granite of the Avdar Massif, Mongolia". TMPM Tschermaks Petr. Mitt. 28 (4): 277–283. Bibcode:1981TMPM...28..277P. doi:10.1007/BF01081855.
  11. ^ Chisholm, Hugh, ed. (1911). "Microcline" . Encyclopædia Britannica. Vol. 18 (11th ed.). Cambridge University Press. p. 380.
  12. ^ "Common Minerals of Virginia". Virginia Department of Mines, Minerals and Energy. Commonwealth of Virginia. Archived from the original on 24 July 2021. Retrieved 5 July 2019.