Amazonite

{{Short description|Green variety of microcline}} {{Infobox mineral |boxbgcolor=#9ef5d8| name = Amazonite | category = Tectosilicate minerals | group = Feldspar group | series = Alkali feldspar series | IMAstatus = Variety of microcline | image = Amazonita1.jpeg | imagesize = 260px | alt = Photo of a turquoise mineral with beige microcline speckled within it | caption = Amazonite from Brazil | formula = KAlSi3O8 | molweight = | strunz = | color = Green, blue-green | habit = Prismatic | system = Triclinic | twinning = | cleavage = Perfect | fracture = Uneven, splintery | mohs = 6.0–6.5 | tenacity = Brittle | luster = Vitreous | refractive = 1.522–1.530 | opticalprop = | birefringence = −0.008 | pleochroism = Absent | dispersion = None | fluorescence = Weak; olive-green | streak = White | gravity = 2.56–2.58 | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent, opaque | other =25px Radioactive 14.05% (K) | references = <ref name="Walter">{{Cite book|url=https://archive.org/details/gemstonesofworld00schu/page/164|title=Gemstones of the world|last=Walter|first=Schumann|date=1997|publisher=Sterling Pub. Co|isbn=0806994614|edition=Rev. & expanded|location=New York|page=[https://archive.org/details/gemstonesofworld00schu/page/164 164]|url-access=registration|via=Internet Archive}}</ref><ref>{{cite web |last= |first= |date= |title=Radioactive Gems : ClassicGems.net |url=https://www.classicgems.net/info_Radioactive.htm |url-status=live |work=ClassicGems.net |location= |archive-url=https://web.archive.org/web/20210211013824/http://classicgems.net/info_Radioactive.htm |archive-date=2021-02-11 |access-date=2021-08-13}}</ref><ref name="bulletin">{{Cite journal|last=Schlegel|first=Dorothy McKenney|date=1957|title=Gem Stones of the United States|url=https://books.google.com/books?id=D78jhspXwxYC|journal=Geological Survey Bulletin|publisher=United States Government Publishing Office|issue=1042-G|via=Google Books}}</ref>:214–215 }}

'''Amazonite''', also known as '''amazonstone''',<ref name="EB1911">{{EB1911|inline=y|wstitle=Amazon-stone|volume=1|page=791}}</ref> is a green tectosilicate mineral, a variety of the potassium feldspar called microcline.<ref name="EB1911"/><ref>{{cite web |url=https://www.gemdat.org/gem-184.html |title=Amazonite gemstone information |website=gemdat.org |access-date=2018-08-24 |url-status=live |archive-url=https://web.archive.org/web/20210301171608/https://www.gemdat.org/gem-184.html |archive-date=2021-03-01}}</ref><ref>{{Cite web |title=Amazonite |url=https://www.mindat.org/min-184.html}}</ref> Its chemical formula is KAlSi3O8,<ref name="Walter" /><ref name="Mindat">{{cite web |url=https://www.mindat.org/min-184.html |title=Amazonite: Amazonite mineral information and data. |website=mindat.org |access-date=13 April 2017 |url-status=live |archive-url=https://web.archive.org/web/20210514154137/https://www.mindat.org/min-184.html |archive-date=14 May 2021}}</ref> which is polymorphic to orthoclase.

The name is derived from the Amazon River, from which green stones were once believed to have been obtained, although it remains uncertain whether those stones were actually amazonite.<ref name="EB1911"/> Although amazonite has been used for jewellery for more than three thousand years, as evidenced by archaeological finds in Middle and New Kingdom Egypt<ref>Harrell and Osman 2007</ref> and Mesopotamia, it is not mentioned by any ancient or medieval sources. It was first described as a distinct mineral in the 18th century.<ref name="Ostrooumov">Mikhail Ostrooumov, ''Amazonite: Mineralogy, Crystal Chemistry, and Typomorphism'' (Elsevier, 2016), p. 1–12.</ref>

Green and greenish-blue varieties of potassium feldspars that are predominantly triclinic are designated as amazonite.<ref name="Pivec1981">{{Cite journal |last1=Pivec |first1=E. |last2=Ševčik |first2=J. |last3=Ulrych |first3=J. |date=December 1981 |title=Amazonite from the alkali granite of the Avdar Massif, Mongolia |journal=TMPM Tschermaks Petr. Mitt. |volume=28 |issue=4 |pages=277–283 |doi=10.1007/BF01081855|bibcode=1981TMPM...28..277P }}</ref> It has been described as a "beautiful crystallized variety of a bright verdigris-green"<ref>{{Cite EB1911|wstitle=Microcline|volume=18|page=380|ref=none}}</ref> and as possessing a "lively green colour".<ref name="EB1911"/> It is occasionally cut and used as a gemstone.<ref>{{cite web|url=https://www.dmme.virginia.gov/dgmr/minerals.shtml|title=Common Minerals of Virginia|website=Virginia Department of Mines, Minerals and Energy|publisher=Commonwealth of Virginia|access-date=5 July 2019|archive-date=24 July 2021|archive-url=https://web.archive.org/web/20210724021345/https://dmme.virginia.gov/dgmr/minerals.shtml|url-status=dead}}</ref>

== Occurrence ==

Amazonite is a mineral of limited occurrence. In Bronze Age Egypt, it was mined in the southern Eastern Desert at Gebel Migif. In early modern times, it was obtained almost exclusively from the area of Miass in the Ilmensky Mountains, {{convert|50|mi|-1}} southwest of Chelyabinsk, Russia, where it occurs in granitic rocks.<ref name="EB1911"/>

Amazonite is now known to occur in various places around the world. Those places are, among others, as follows:

Australia:

* Eyre Peninsula, Koppio, Baila Hill Mine (Koppio Amazonite Mine)<ref>{{Cite web |title=Barnes L. C., et al, (1980), Some Semiprecious and Ornamental Stones of South Australia, Government Printer, Adelaide, South Australia. |url=https://www.mindat.org/reference.php?id=15954600}}</ref>

China: * Baishitouquan granite intrusion, Hami Prefecture, Xinjiang: found in granite<ref>{{Cite journal|last1=Yang|first1=Jianye|last2=Zhao|first2=Lei|last3=Zhang|first3=Weiguo|date=April 2014|title=The Geochemical Effect of Lanthanides: Its Types and Application for Magmatic Rocks—A New Method to Semi-Quantitatively Determine Strength of Magmatic Fluid Complexation and Fractional Crystallization|url=http://en.earth-science.net/PDF/20140514043208.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://en.earth-science.net/PDF/20140514043208.pdf |archive-date=2022-10-09 |url-status=live|journal=Journal of Earth Science|publisher=China University of Geosciences (Wuhan)|volume=25|issue=2|pages=252–262|doi=10.1007/s12583-014-0420-z|s2cid=54836739|issn=1674-487X}}</ref><ref>{{Cite journal|last1=Sihai|first1=Liu|last2=Changzhi|first2=Wu|last3=Lianxing|first3=Gu|last4=Zunzhong|first4=Zhang|last5=Junhua|first5=Tang|last6=Guangrong|first6=Li|last7=Ruxiong|first7=Lei|last8=Chuansheng|first8=Wang|date=2008|title=中天山白石头泉岩体年代学、岩石成因及构造意义|trans-title=Geochronology, petrogenesis and tectonic significances of the Baishitouquan pluton in Middle Tianshan, Northwest China|url=http://www.ysxb.ac.cn/ysxb/ch/reader/create_pdf.aspx?file_no=20081206&year_id=2008&quarter_id=12&falg=1|journal=Acta Petrologica Sinica|language=zh|location=Beijing|publisher=China Science Publishing & Media Ltd.|volume=24|issue=11|pages=2720|issn=1000-0569}}</ref> Libya: * Jabal Eghei, Tibesti Mountains: found in granitic rocks<ref>{{Cite journal|last1=Suayah|first1=Ismail B.|last2=Miller|first2=Jonathan S.|last3=Miller|first3=Brent V.|last4=Bayer|first4=Tovah M.|last5=Rogers|first5=John J.W.|s2cid=26947582|date=April 2006|title=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=Journal of African Earth Sciences|volume=44|issue=4–5|pages=564|doi=10.1016/j.jafrearsci.2005.11.020|bibcode=2006JAfES..44..561S|issn=1464-343X|display-authors=3}}</ref> Mongolia: * Avdar Massif, Töv Province: found in alkali granite<ref name="Pivec1981"/>

Ethiopia: * Konso Zone

South Africa:

* Mogalakwena, Limpopo Province<ref name=":0">{{Cite web|title=Amazonite from South Africa|url=https://www.mindat.org/locentries.php?p=14468&m=184|website=www.mindat.org|access-date=2020-05-25}}</ref> * Khâi-Ma, Northern Cape<ref name=":0" /> * Kakamas, Northern Cape<ref name=":0" /> * Ceres Valley, Western Cape<ref name=":0" />

Sweden: *Skuleboda mine, Västra Götaland County: found in pegmatite<ref name=Almq>{{Cite book|title=Nyttosten i Sverige|last1=Lundegårdh|first1=Per H.|publisher=Almqvist & Wiksell|year=1971|isbn=|location=Stockholm|language=Swedish|pages=21}}</ref>

United States: * Colorado: ** Deer Trail, Arapahoe County<ref name="bulletin"/>:233 ** Custer County<ref name="bulletin"/>:234 ** Devils Head, Douglas County<ref name="bulletin"/>:234 ** Pine Creek, Douglas County<ref name="bulletin"/>:234 ** Crystal Park, El Paso County<ref name="bulletin"/>:234 ** Pikes Peak, El Paso County: found in coarse granites or pegmatite<ref name="EB1911"/> ** St. Peter's Dome, El Paso County<ref name="bulletin"/>:234 ** Tarryall Mountains, Park County<ref name="bulletin"/>:235 ** Crystal Peak, Teller County<ref name="bulletin"/>:235 * Wyoming * Virginia: ** Morefield Mine, Amelia County: found in pegmatite<ref name="virginia_minerals">{{Cite journal|last1=Penick|first1=D. Allen Jr.|last2=Sweet|first2=Palmer C.|date=May 1992|title=Mineral collecting sites in Virginia|url=http://www.dmme.virginia.gov/DMR3/dmrpdfs/vamin/VAMIN_VOL38_NO02.pdf|url-status=dead|journal=Virginia Minerals|location=Charlottesville, Virginia|publisher=Virginia Department of Mines, Minerals, and Energy|volume=38|issue=2|pages=10–12|archive-url=https://web.archive.org/web/20120424152733/http://www.dmme.virginia.gov/DMR3/dmrpdfs/vamin/VAMIN_VOL38_NO02.pdf|archive-date=24 April 2012}}</ref> ** Rutherford Mine, Amelia County<ref name="virginia_minerals"/> * Pennsylvania: ** Media, Delaware County<ref name="bulletin"/>:244 ** Middletown, Delaware County<ref name="bulletin"/>:244

== Color ==

For many years, the source of amazonite's color was a mystery.<ref name="mineralogist"/> Some people assumed the color was due to copper because copper compounds often have blue and green colors.<ref name="mineralogist">{{cite journal | url=http://www.minsocam.org/ammin/AM70/AM70_794.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.minsocam.org/ammin/AM70/AM70_794.pdf |archive-date=2022-10-09 |url-status=live | author=Hoffmeister and Rossman | title=A spectroscopic study of irradiation coloring of amazonite; structurally hydrous, Pb-bearing feldspar | journal=American Mineralogist | year=1985 | volume=70 | pages=794–804 | via=Mineralogical Society of America}}</ref> A 1985 study suggests that the blue-green color results from quantities of lead and water in the feldspar.<ref name="mineralogist"/> Subsequent 1998 theoretical studies by A. Julg expand on the potential role of aliovalent lead in the color of microcline.<ref name="Julg">{{Cite journal|last=Julg|first=A.|date=February 1998|title=A theoretical study of the absorption spectra of Pb+ and Pb3+ in site K+ of microcline: application to the color of amazonite|journal=Physics and Chemistry of Minerals|publisher=Springer-Verlag|volume=25|issue=3|pages=229–233|doi=10.1007/s002690050108|bibcode=1998PCM....25..229J|s2cid=95011489|issn=1432-2021}}</ref>

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.<ref name="Pivec1981"/> A 2010 study also implicated the role of divalent iron in the green coloration.<ref name="Mindat"/> These studies and associated hypotheses indicate the complex nature of the color in amazonite; in other words, the color may be the aggregate effect of several mutually inclusive and necessary factors.<ref name="Ostrooumov"/>

== Health == A 2021 study by the German Institut für Edelsteinprüfung (EPI) found that the amount of lead ions that leaked from an {{convert|11|g|oz|abbr=on}} sample of amazonite into an acidic solution simulating saliva exceeded European Union standard DIN EN 71-3:2013's recommended amount by five times. This experiment was to simulate a child swallowing amazonite, and could also apply to "crystal healing" practices such as inserting the mineral into drinking water bottles.<ref>{{cite news |last= |first= |date=April 22, 2021 |title=Lead in Amazonite – Caution |url=https://www.epigem.de/en-us/toxic-minerals/lead-in-amazonite-caution.html |url-status=live |work=Institut für Edelsteinprüfung |location= |archive-url=https://web.archive.org/web/20210307075548/https://epigem.de/en-us/toxic-minerals/lead-in-amazonite-caution.html |archive-date=March 7, 2021 |access-date=August 13, 2021}}</ref>

== Gallery == <gallery widths="130" heights="150">

File:Microcline-Quartz-Albite-48224.jpg|Deep robins-egg blue color amazonite crystal on smoky quartz and albite, from Teller County, Colorado. Size: {{cvt|3.4|x|3.3|x|2.5|cm|1}}. File:Amazonite, quartz 300-3-7927.JPG|Amazonite crystal on smoky quartz, from Pikes Peak, El Paso County, Colorado File:Microcline-179612.jpg|Large deep-turquoise amazonite crystal with attached stark-white microcline, from Konso, SNNPR, Ethiopia. Size: {{cvt|16.4|x|11.9|x|8.0|cm|1}}. File:Microcline-Quartz-206935.jpg|Two smoky quartz crystals surrounded by amazonite crystals, from Smoky Hawk Mine, Crystal Peak, Teller County, Colorado. Size: {{cvt|11.0|x|8.2|x|6.3|cm|1}}. File:Amazonite 1.jpg|Amazonite crystals on orthoclase, from Konso, SNNPR, Ethiopia. File:Microcline-20436.jpg|Deep lustrous crystal of amazonite, from Take 5 Claim, Crystal Peak, Teller County, Colorado. Size: {{cvt|4.4|x|4.0|x|3.5|cm|1}}. File:Landsverk-1 amazonite+ordførerkjede.jpg|Amazonite from the Landsverk 1 mine with the livery collar of the mayor of Evje, Norway. Size: {{cvt|21|x|22|cm}}. File:LANDSVERK-1 mikroklien-verdringt-amazoniet.jpg|Amazonite partly altered to brown microcline from the Landsverk 1 mine in Evje, Norway. File:Amazonite specimen (polished) arp.jpg|Polished Amazonite specimen. Height {{cvt|13|cm|0}}. </gallery>

== References == {{Reflist}}

== Further reading == *{{cite book |last=Perl |first=Richard M. |title=Colorado Gem Trails: And Mineral Guide |year=1972 |publisher=Swallow Press |isbn=978-0-8040-0956-0}}

== External links == {{Commons-inline}}

Category:Alkali feldspar series Category:Gemstones Category:Aluminosilicates