Editing Turquoise (section)

{{Short description|Opaque, blue-to-green mineral}}
{{About|the mineral|the color|Turquoise (color)|5=Turquoise (disambiguation)}}
{{more citations needed|date=June 2022}}
{{Infobox mineral
| name        = Turquoise
| category    = [[Phosphate mineral]]s
| boxwidth    =
| boxbgcolor  =#00CED1
| image       = Turquoise-40031.jpg
| caption     = 
| formula     = {{chem2|CuAl6(PO4)4(OH)8*4H2O}}
| IMAsymbol   = Tqu<ref>{{cite journal |last=Warr|first=L. N. |date=2021 |title=IMA–CNMNC approved mineral symbols |journal=[[Mineralogical Magazine]] |volume=85 |issue=3 |pages=291–320 |doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616|doi-access=free }}</ref>
| strunz      = 8.DD.15
| system      = [[triclinic crystal system|Triclinic]]
| class       = Pinacoidal ({{Overline|1}}) <br /><small>(same [[H–M symbol]])</small>
| colour      = [[turquoise (color)|Turquoise]], blue, [[blue-green]], green
| habit       = Massive, nodular
| twinning    =
| cleavage    = Perfect on {001}, good on {010}, but cleavage rarely seen
| fracture    = [[conchoidal fracture|Conchoidal]]
| mohs        = 5–6
| luster     = Waxy to subvitreous
| refractive  = ''n<sub>α</sub>'' = 1.610<br />''n<sub>β</sub>'' = 1.615<br />''n<sub>γ</sub>'' = 1.650
| opticalprop = Biaxial (+)
| birefringence = +0.040
| pleochroism = Weak
| streak      = Bluish white
| gravity     = 2.6–2.9
| melt        =
| fusibility  = Fusible in heated [[hydrochloric acid|HCl]]
| diagnostic  =
| solubility  = Soluble in [[hydrochloric acid|HCl]]
| diaphaneity = [[opacity (optics)|Opaque]]
| references  =<ref name="Hurlbut">{{cite book |last1=Hurlbut|first1=Cornelius S. |last2=Klein|first2=Cornelis |year=1985 |title=Manual of Mineralogy |edition=20th |publisher=[[Wiley (publisher)|John Wiley & Sons]] |location=New York |isbn=978-0-471-80580-9 |url-access=registration |url=https://archive.org/details/manualofmineralo00klei}}</ref><ref name="mindat">{{Mindat |id=4060 |name=Turquoise |access-date=2006-10-04}}. {{Cite web |url=http://www.mindat.org/min-4060.html |title=Turquoise: Turquoise mineral information and data |access-date=2006-10-04 |archive-date=2006-11-12 |archive-url=https://web.archive.org/web/20061112155323/http://www.mindat.org/min-4060.html |url-status=bot: unknown }}.</ref><ref name="rruff">{{cite book |editor1-last=Anthony |editor1-first=John W. |editor2-last=Bideaux |editor2-first=Richard A. |editor3-last=Bladh |editor3-first=Kenneth W. |editor4-last=Nichols |editor4-first=Monte C. |title=Handbook of Mineralogy |publisher=[[Mineralogical Society of America]] |location=[[Chantilly, Virginia]] |chapter-url=http://rruff.info/doclib/hom/turquoise.pdf |chapter=Turquoise |isbn=978-0-9622097-3-4 |volume=IV |year=2000 |url-status=live |archive-url=https://web.archive.org/web/20120211163838/http://rruff.geo.arizona.edu/doclib/hom/turquoise.pdf |archive-date=2012-02-11 }}</ref>
}}

'''Turquoise''' is an [[opacity (optics)|opaque]], [[blue-green|blue-to-green]] [[mineral]] that is a [[hydrate|hydrous]] [[phosphate]] of [[copper]] and [[aluminium]], with the [[chemical formula]] {{chem2|[[copper|Cu]][[aluminium|Al]]6([[phosphate|PO4]])4([[hydroxide|OH]])8*4[[water|H2O]]}}. It is rare and valuable in finer grades and has been prized as a [[gemstone]] for millennia due to its hue.

The [[robin egg blue]] or [[sky blue]] color of the [[Iran|Persian]] turquoise mined near the modern city of [[Nishapur]], [[Iran]], has been used as a guiding reference for evaluating turquoise quality.<ref>{{cite web |title=Turquoise Quality Factors |url=https://gia.edu/turquoise-quality-factor |publisher=[[Gemological Institute of America]]}}</ref>

Like most other opaque gems, turquoise has been devalued by the introduction of treatments, imitations, and synthetics into the market.