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amazonite

{{Short description|Green variety of microcline, tectosilicate mineral}}

{{Infobox mineral

|boxbgcolor=#9ef5d8| name = Amazonite

| category = Tectosilicate minerals, feldspar group, alkali series, microcline variety

| 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 = {{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}}{{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}}{{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}}:214–215

}}

Amazonite, also known as amazonstone,{{EB1911|inline=y|wstitle=Amazon-stone|volume=1|page=791}} is a green tectosilicate mineral, a variety of the potassium feldspar called microcline.{{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}}{{Cite web |title=Amazonite |url=https://www.mindat.org/min-184.html}} Its chemical formula is KAlSi3O8,{{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}} 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. Although it has been used for jewellery for well over three thousand years, as attested by archaeological finds in Middle and New Kingdom EgyptHarrell and Osman 2007 and Mesopotamia, no ancient or medieval authority mentions it. It was first described as a distinct mineral only in the 18th century.Mikhail Ostrooumov, Amazonite: Mineralogy, Crystal Chemistry, and Typomorphism (Elsevier, 2016), p. 1–12.

Green and greenish-blue varieties of potassium feldspars that are predominantly triclinic are designated as amazonite.{{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 }} It has been described as a "beautiful crystallized variety of a bright verdigris-green"{{Cite EB1911|wstitle=Microcline|volume=18|page=380|ref=none}} and as possessing a "lively green colour". It is occasionally cut and used as a gemstone.{{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}}

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.

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){{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}}

China:

  • Baishitouquan granite intrusion, Hami Prefecture, Xinjiang: found in granite{{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}}{{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}}

Libya:

  • Jabal Eghei, Tibesti Mountains: found in granitic rocks{{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}}

Mongolia:

Ethiopia:

South Africa:

  • Mogalakwena, Limpopo Province{{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}}
  • Khâi-Ma, Northern Cape
  • Kakamas, Northern Cape
  • Ceres Valley, Western Cape

Sweden:

United States:

Color

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.{{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}} A 1985 study suggests 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.{{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}}

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 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 color may be the aggregate effect of several mutually inclusive and necessary factors.

Health

A 2021 study by the German Institut für Edelsteinprüfung (EPI) found that the amount of lead 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 new alternative medicine practices such as inserting the mineral into oils or drinking water for days.{{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}}

Gallery

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}}.

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

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Category:Feldspar

Category:Gemstones