Editing Turquoise (section)

== Treatments ==
{{more citations needed section|date=June 2022}}
[[File:Madan Turquoise Mines.jpg|thumb|An early turquoise mine in Madan, [[Khorasan Province]], Iran]]
Turquoise is treated to enhance both its colour and durability (increased [[hardness]] and decreased [[porosity]]). As is so often the case with any precious stones, full disclosure about treatment is frequently not given. [[Gemology|Gemologists]] can detect these treatments using a variety of testing methods, some of which are destructive, such as the use of a heated probe applied to an inconspicuous spot, which will reveal oil, wax or plastic treatment.

=== Waxing and oiling ===
Historically, light waxing and oiling were the first treatments used in ancient times, providing a wetting effect, thereby enhancing the colour and lustre. This treatment is more or less acceptable by tradition, especially because treated turquoise is usually of a higher grade to begin with. Oiled and waxed stones are prone to "sweating" under even gentle heat or if exposed to too much sun, and they may develop a white surface film or bloom over time. (With some skill, oil and wax treatments can be restored.)

=== Backing ===
Since finer turquoise is often found as thin seams, it may be [[adhesive|glued]] to a base of stronger foreign material for reinforcement. These stones are termed "backed", and it is standard practice that all thinly cut turquoise in the Southwestern United States is backed. [[Native Americans in the United States|Native indigenous peoples]] of this region, because of their considerable use and wearing of turquoise, have found that backing increases the durability of thinly cut slabs and cabochons of turquoise. They observe that if the stone is not backed it will often crack. Backing of turquoise is not widely known outside of the [[Indigenous peoples of the Americas|Native American]] and Southwestern United States jewellery trade. Backing does not diminish the value of high quality turquoise, and indeed the process is expected for most thinly cut American commercial gemstones.{{Citation needed|date=June 2007}}

=== Zachery treatment===
A proprietary process was created by electrical engineer and turquoise dealer James E. Zachery in the 1980s to improve the stability of medium to high-grade turquoise. The process can be applied in several ways: either through deep penetration on rough turquoise to decrease porosity, by shallow treatment of finished turquoise to enhance color, or both. The treatment can enhance color and improve the turquoise's ability to take a polish. Such treated turquoise can be distinguished in some cases from natural turquoise, without destruction, by [[energy-dispersive X-ray spectroscopy]], which can detect its elevated potassium levels. In some instances, such as with already high-quality, low-porosity turquoise that is treated only for porosity, the treatment is undetectable.<ref>{{cite journal |last1=Fritsch |first1=Emmanuel |last2=McClure |first2=Shane F. |last3=Ostrooumov |first3=Mikhail |last4=Andres |first4=Yves |last5=Moses |first5=Thomas |last6=Koivula |first6=John I. |last7=Kammerling |first7=Robert C. |title=The identification of Zachery-treated turquoise |journal=Gems & Gemology |date=Spring 1999 |volume=35 |pages=4–16 |doi=10.5741/GEMS.35.1.4 |url=https://www.gia.edu/doc/The-Identification-of-Zachery-Treated-Turquoise.pdf |access-date=14 May 2022}}</ref><ref name="Schwarzinger22017">{{cite journal |last1=Schwarzinger |first1=Bettina |last2=Schwarzinger |first2=Clemens |title=Investigation of turquoise imitations and treatment with analytical pyrolysis and infrared spectroscopy |journal=Journal of Analytical and Applied Pyrolysis |date=May 2017 |volume=125 |pages=24–31 |doi=10.1016/j.jaap.2017.05.002}}</ref>

=== Dyeing ===
The use of [[Prussian blue]] and other dyes (often in conjunction with bonding treatments) to "enhance” its appearance, make uniform or completely change the colour, is regarded as fraudulent by some purists,<ref name="Purists" /> especially since some dyes may fade or rub off on the wearer. Dyes have also been used to darken the veins of turquoise.

=== Stabilization ===
Material treated with plastic or water glass is termed "bonded" or "stabilized" turquoise. This process consists of pressure impregnation of otherwise unsaleable chalky American material by [[epoxy]] and [[plastic]]s (such as [[polystyrene]]) and [[water glass]] (sodium silicate) to produce a wetting effect and improve durability. Plastic and water glass treatments are far more permanent and stable than waxing and oiling, and can be applied to material too chemically or physically unstable for oil or wax to provide sufficient improvement. Conversely, stabilization and bonding are rejected by some as too radical an alteration.<ref name="Purists">{{cite web |url=http://www.geocities.com/harriss75007/turquois.htm |title=Tantalizing Turquoise|last=Harriss|first= Joseph A. | access-date = 2007-06-01 |archive-url=https://web.archive.org/web/20080201025038/http://www.geocities.com/harriss75007/turquois.htm|archive-date=2008-02-01}}</ref>

The epoxy binding technique was first developed in the 1950s and has been attributed to Colbaugh Processing of Arizona, a company that still operates today.

=== Reconstitution ===
Perhaps the most extreme of treatments is "reconstitution", wherein fragments of fine turquoise material, too small to be used individually, are powdered and then bonded with resin to form a solid mass. Very often the material sold as "reconstituted turquoise" is [[#Imitations|artificial]], with little or no natural stone, made entirely from resins and dyes. In the trade reconstituted turquoise is often called "block turquoise" or simply "block".