Editing Cubic zirconia

{{Short description|Cubic crystalline form of zirconium dioxide}}
{{Distinguish|Zircon|zirconia|zirconium|synthetic diamonds}}
{{For|the electronic group|Cubic Zirconia (band)}}
{{Use dmy dates|date=May 2018}}
{{More citations needed|date=January 2008}}
{{Infobox mineral
|boxbgcolor=#DAF7A6
| name        = Cubic zirconia
| category    = {{plainlist|
* [[Oxide minerals]]
}}
| image       = CZ brilliant.jpg
| imagesize   = 260px
| caption     = A round [[Brilliant (diamond cut)|brilliant-cut]] cubic zirconia
| formula     = 
| strunz      = 
| system      = [[Cubic crystal system|Cubic]]
| class       = 
| symmetry    = 
| unit cell   = 
| color       = Various
| habit       = 
| twinning    = 
| cleavage    = 
| fracture    = 
| mohs        = 8.0–8.5
| luster      = 
| refractive  = 2.15–2.18
| opticalprop = 
| birefringence =
| pleochroism = 
| streak      = 
| gravity     = 5.6–6.0 g/cm3

| fusibility  =
| diagnostic  =
| solubility  = 
| diaphaneity = 
| other       = 
| references  = 
}}

'''Cubic zirconia''' (abbreviated ''CZ'') is the cubic crystalline form of [[zirconium dioxide]] (ZrO<sub>2</sub>). The synthesized material is hard and usually colorless, but may be made in a variety of different colors. It should not be confused with [[zircon]], which is a [[zirconium silicate]] (ZrSiO<sub>4</sub>). It is sometimes erroneously called ''cubic zirconium''.

Because of its low cost, durability, and close visual likeness to [[diamond]], synthetic cubic zirconia has remained the most [[gemology|gemologically]] and economically important competitor for diamonds since commercial production began in 1976. Its main competitor as a synthetic [[gemstone]] is a more recently cultivated material, synthetic [[moissanite]].

==Technical aspects==
Cubic zirconia is [[crystallography|crystallographically]] [[Cubic crystal system|isometric]], an important attribute of a would-be [[diamond simulant]]. During synthesis zirconium oxide naturally forms [[monoclinic]] [[crystal]]s, which are stable under normal atmospheric conditions. A stabilizer is required for cubic crystals (taking on the [[fluorite structure]]) to form, and remain stable at ordinary temperatures; typically this is either [[yttrium]] or [[calcium]] oxide, the amount of stabilizer used depending on the many recipes of individual manufacturers. Therefore, the physical and optical properties of synthesized CZ vary, all values being ranges.

It is a dense substance, with a [[density]] between 5.6 and 6.0&nbsp;g/cm<sup>3</sup>—about 1.65 times that of diamond. Cubic zirconia is relatively hard, 8–8.5 on the [[Mohs scale of mineral hardness|Mohs scale]]—slightly harder than most semi-precious natural [[gemstone|gems]].<ref name="Mohs' Hardness of Abrasives">{{cite web| url = http://www.reade.com/resources/reference-charts-particle-property-briefings/851-mohs-hardness-of-abrasives| title = Mohs' Hardness of Abrasives| access-date = 6 June 2009| url-status = dead| archive-url = https://web.archive.org/web/20091017120910/http://www.reade.com/resources/reference-charts-particle-property-briefings/851-mohs-hardness-of-abrasives| archive-date = 17 October 2009| df = dmy-all}}</ref> Its [[refractive index]] is high at 2.15–2.18 (compared to 2.42 for diamonds) and its [[Lustre (mineralogy)|luster]] is [[Lustre (mineralogy)#Adamantine lustre|Adamantine lustre]]. Its [[dispersion (optics)|dispersion]] is very high at 0.058–0.066, exceeding that of diamond (0.044). Cubic zirconia has no [[cleavage (crystal)|cleavage]] and exhibits a [[conchoidal fracture]]. Because of its high hardness, it is generally considered  [[Brittleness|brittle]].

Under shortwave [[UV]] cubic zirconia typically [[fluorescence|fluoresces]] a yellow, greenish yellow or "beige". Under longwave UV the effect is greatly diminished, with a whitish glow sometimes being seen. Colored stones may show a strong, complex [[rare earth element|rare earth]] [[absorption spectrum]].

==History==
Discovered in 1892, the yellowish monoclinic mineral [[baddeleyite]] is a natural form of zirconium oxide.<ref name= Bayanova/>

The high melting point of zirconia (2750&nbsp;°C or 4976&nbsp;°F) hinders controlled growth of single crystals. However, stabilization of cubic zirconium oxide had been realized early on, with the synthetic product ''stabilized zirconia'' introduced in 1929. Although cubic, it was in the form of a [[polycrystalline]] [[ceramic]]: it was used as a [[refractory]] material, highly resistant to chemical and thermal attack (up to 2540&nbsp;°C or 4604&nbsp;°F).<ref name=growth/>

In 1937, German [[mineralogy|mineralogists]] M. V. Stackelberg and K. Chudoba discovered naturally occurring cubic zirconia in the form of microscopic grains included in [[Metamictisation|metamict]] zircon. This was thought to be a byproduct of the metamictization process, but the two scientists did not think the mineral important enough to give it a formal name. The discovery was confirmed through [[X-ray diffraction]], proving the existence of a natural counterpart to the synthetic product.<ref name=chudoba/><ref name=chic>{{cite web|title=Understanding more about Cubic Zirconia|url=http://chicjewelry.com/blog/understanding-more-about-cubic-zirconia/|publisher=Chic Jewelry|access-date=6 December 2013|year=2013|url-status=dead|archive-url=https://web.archive.org/web/20131214145340/http://chicjewelry.com/blog/understanding-more-about-cubic-zirconia/|archive-date=14 December 2013|df=dmy-all}}</ref>

As with the majority of [[crystal growth|grown]] [[Diamond simulant|diamond substitutes]], the idea of producing single-crystal cubic zirconia arose in the minds of scientists seeking a new and versatile material for use in [[lasers]] and other optical applications. Its production eventually exceeded that of earlier synthetics, such as synthetic [[strontium titanate]], synthetic [[rutile]], [[Yttrium aluminium garnet|YAG]] ([[yttrium]] [[aluminium]] [[garnet]]) and [[gadolinium gallium garnet|GGG]] ([[gadolinium]] [[gallium]] garnet).

Some of the earliest research into controlled single-crystal growth of cubic zirconia occurred in 1960s France, much work being done by Y. Roulin and R. Collongues. This technique involved molten zirconia being contained within a thin shell of still-solid zirconia, with crystal growth from the melt. The process was named ''cold crucible'', an allusion to the system of water cooling used. Though promising, these attempts yielded only small crystals.

Later, [[Soviet Union|Soviet]] scientists under V. V. Osiko in the [[Laser]] Equipment Laboratory at the [[Lebedev Physical Institute]] in Moscow perfected the technique, which was then named ''[[skull crucible]]'' (an allusion either to the shape of the water-cooled container or to the form of crystals sometimes grown). They named the jewel ''Fianit'' after the institute's name [[Lebedev Physical Institute|FIAN]] (Physical Institute of the Academy of Science), but the name was not used outside of the USSR.{{citation needed|date=April 2021}} This was known at the time as the Institute of Physics at the Russian Academy of Science.<ref name="rscz">{{cite news |title=Cubic Zirconia |url=https://rusgems.org/products/1/fianit/ |access-date=3 April 2021 |publisher=RusGems |archive-date=28 April 2021 |archive-url=https://web.archive.org/web/20210428004700/https://rusgems.org/products/1/fianit/ |url-status=dead }}</ref> Their breakthrough was published in 1973, and commercial production began in 1976.<ref name=Hesse/> In 1977, cubic zirconia began to be mass-produced in the jewelry marketplace by the Ceres Corporation, with crystals stabilized with 94% yttria. Other major producers as of 1993 include [[Taiwan Crystal Company Ltd]], [[Swarovski]] and ICT inc.<ref name=":0">{{cite book |last1=Stuart |first1=Sam |chapter=Glass and Gemstones |pages=91–93 |chapter-url=https://books.google.com/books?id=OisXBQAAQBAJ&pg=PA91 |title=Zirconia |date=2013 |publisher=Elsevier |isbn=978-1-4831-9400-4 }}</ref><ref name=chic/> By 1980, annual global production had reached 60 million [[Carat (unit)|carats]] (12 tonnes) and continued to increase, with production reaching around 400 tonnes per year in 1998.<ref name=":0" />

Because the natural form of cubic zirconia is so rare, all cubic zirconia used in jewelry has been synthesized, one method of which was [[patent]]ed by Josep F. Wenckus & Co. in 1997.<ref>{{cite patent |country=US|number=4488821 |status=Patent |title=Method and means of rapidly distinguishing a simulated diamond from natural diamond |gdate=1984-12-18}}</ref><ref>{{Cite web|url=https://jewelrymaterialguide.com/cubic-zirconia-vs-zircon/|title=Cubic Zirconia VS Zircon - 6 Ways To Tell Them Apart|first=Ioana|last=Ciuraru|date=2 February 2022}}</ref><ref>{{Cite web|url=https://gioiellis.com/en/tag/zircon/|title=zirconi Archives &#124; gioiellis.com|date=25 April 2024|website=gioiellis.com}}</ref>

==Synthesis==
[[Image:1000kwCZLpKelley.jpg|thumb|Worker monitoring melting zirconium oxide and yttrium oxide in an induction-heated "cold crucible" to create cubic zirconia]]

The skull-melting method refined by Josep F. Wenckus and coworkers in 1997 remains the industry standard. This is largely due to the process allowing for temperatures of over 3000 &nbsp;°C to be achieved, lack of contact between crucible and material as well as the freedom to choose any gas atmosphere. Primary downsides to this method include the inability to predict the size of the crystals produced and it is impossible to control the crystallization process through temperature changes.<ref name="growth" /><ref name=":1" />

The apparatus used in this process consists of a cup-shaped crucible surrounded by radio frequency-activated (RF-activated) copper coils and a water-cooling system.<ref name="growth" /><ref name=":2" />

Zirconium dioxide thoroughly mixed with a stabilizer (normally 10% [[Yttrium(III) oxide|yttrium oxide]]) is fed into a cold crucible. Metallic chips of either zirconium or the stabilizer are introduced into the powder mix in a compact pile manner. The RF generator is switched on and the metallic chips quickly start heating up and readily oxidize into more zirconia. Consequently, the surrounding powder heats up by thermal conduction, begins melting and, in turn, becomes electroconductive, and thus it begins to heat up via the RF generator as well. This continues until the entire product is molten. Due to the cooling system surrounding the crucible, a thin shell of sintered solid material is formed. This causes the molten zirconia to remain contained within its own powder which prevents it from being contaminated from the crucible and reduces heat loss. The melt is left at high temperatures for some hours to ensure homogeneity and ensure that all impurities have evaporated. Finally, the entire crucible is slowly removed from the RF coils to reduce the heating and let it slowly cool down (from bottom to top). The rate at which the crucible is removed from the RF coils is chosen as a function of the stability of crystallization dictated by the phase transition diagram. This provokes the crystallization process to begin and useful crystals begin to form. Once the crucible has been completely cooled to room temperature, the resulting crystals are multiple elongated-crystalline blocks.<ref name=":1" /><ref name=":2" />

This shape is dictated by a concept known as crystal degeneration according to Tiller. The size and diameter of the obtained crystals is a function of the cross-sectional area of the crucible, volume of the melt and composition of the melt.<ref name="growth" /> The diameter of the crystals is heavily influenced by the concentration of Y<sub>2</sub>O<sub>3</sub> stabilizer.

=== Phase relations in zirconia solids solutions  ===
As seen on the [[phase diagram]], the cubic phase will crystallize first as the solution is cooled down no matter the [[concentration]] of Y<sub>2</sub>O<sub>3</sub>. If the concentration of Y<sub>2</sub>O<sub>3</sub> is not high enough the cubic structure will start to break down into the tetragonal state which will then break down into a monoclinic phase. If the concentration of Y<sub>2</sub>O<sub>3</sub> is between 2.5-5% the resulting product will be PSZ (partially stabilized zirconia) while monophasic cubic crystals will form from around 8-40%. Below 14% at low growth rates tend to be opaque indicating partial phase separation in the solid solution (likely due to diffusion in the crystals remaining in the high temperature region for a longer time). Above this threshold crystals tend to remain clear at reasonable growth rates and maintains good annealing conditions.<ref name=":1" />

=== Doping ===
Because of cubic zirconia's isomorphic capacity, it can be doped with several elements to change the color of the crystal. A list of specific dopants and colors produced by their addition can be seen below.

{| class="wikitable" border="1"
|-
!Dopant<ref name=":1">{{cite book |doi=10.1002/0470871687.ch21 |chapter=Growth of Zirconia Crystals by Skull-Melting Technique |title=Crystal Growth Technology |date=2003 |last1=Lomonova |first1=E. E. |last2=Osiko |first2=V. V. |pages=461–485 |isbn=978-0-471-49059-3 }}</ref><ref name=":2">{{cite journal |last1=Nassau |first1=Kurt |title=Cubic Zirconia: An Update |journal=Gems & Gemology |date=Spring 1981 |volume=17 |issue=1 |pages=9–19 |doi=10.5741/GEMS.17.1.9 }}</ref>
!Symbol
!Color(s)
|-
|[[Cerium]]
|Ce
| yellow-orange-red
|-
|[[Chromium]]
|Cr
|green
|-
|[[Cobalt]]
|Co
|lilac-violet-blue
|-
|[[Copper]]
|Cu
|yellow-aqua
|-
|[[Erbium]]
|Er
|pink
|-
|[[Europium]]
|Eu
|pink
|-
|[[Iron]]
|Fe
|yellow
|-
|[[Holmium]]
|Ho
|Champagne
|-
|[[Manganese]]
|Mn
|brown-violet
|-
|[[Neodymium]]
|Nd
| purple
|-
|[[Nickel]]
|Ni
|yellow-brown
|-
|[[Praseodymium]]
|Pr
|amber
|-
|[[Thulium]]
|Tm
|yellow-brown
|-
|[[Titanium]]
|Ti
|golden brown
|-
|[[Vanadium]]
|V
|green
|}
{| class="wikitable"
|+
!Color Range<ref name=":1" /><ref name=":2" />
!Dopant Used
|-
|yellow-orange-red
|<chem>CeO2 
</chem>, <chem>Ce2O3</chem>
|-
|yellow-amber-brown
|'''<chem>CuO, Fe2O3, NiO, Pr2O3, TiO2</chem>'''
|-
|pink
|<chem>Er2O3, Eu2O3, Ho2O3</chem>
|-
|green-olive
|<chem>Cr2O3, Tm2O3, V2O3</chem>
|-
|lilac-violet
|<chem>Co2O3, MnO2, Nd2O3</chem>
|}
<gallery>
Image:Baguette Double Side Checkerboard Cut CZ.JPG|Purple cubic zirconia with checkerboard cut
Image:Multicolor Cubic zirconia.JPG|Multi-color cubic zirconia
Image:Multi Colour CubicZirconia.JPG|Three-tone cubic zirconia gems
Image:Yellow cubic zirconia.JPG|Yellow cubic zirconia
</gallery>

=== Primary growth defects ===
The vast majority of YCZ (yttrium bearing cubic zirconia) crystals are clear with high optical perfection and with gradients of the refractive index lower than <math>5\times 10^{-5}</math>.<ref name=":1" /> However some samples contain defects with the most characteristic and common ones listed below.

* Growth striations: These are located perpendicular to the growth direction of the crystal and are caused mainly by either fluctuations in the crystal growth rate or the non-congruent nature of liquid-solid transition, thus leading to non-uniform distribution of Y<sub>2</sub>O<sub>3</sub>.
* Light-scattering phase inclusions: Caused by contaminants in the crystal (primarily precipitates of silicates or aluminates of yttrium), typically of magnitude 0.03-10 μm.
* Mechanical stresses: Typically caused by the high temperature gradients of the growth and cooling processes, causing the crystal to form with internal mechanical stresses acting on it. This causes refractive index values of up to <math display="inline">8\times 10^{-4}</math>, although the effect of this can be reduced by annealing at 2100&nbsp;°C followed by a slow enough cooling process.
* Dislocations: Similar to mechanical stresses, dislocations can be greatly reduced by annealing.

== Uses outside jewelry ==
Due to its optical properties yttrium cubic zirconia (YCZ) has been used for windows, lenses, prisms, filters and laser elements. Particularly in the chemical industry it is used as window material for the monitoring of corrosive liquids due to its chemical stability and mechanical toughness. YCZ has also been used as a substrate for semiconductor and superconductor films in similar industries.<ref name=":1"/>

Mechanical properties of partially stabilized zirconia (high hardness and shock resistance, low friction coefficient, high chemical and thermal resistance as well as high wear and tear resistance) allow it to be used as a very particular building material, especially in the bio-engineering industry: It has been used to make reliable super-sharp medical scalpels for doctors that are compatible with bio-tissues and contain an edge much smoother than one made of steel.<ref name=":1"/>

==Innovations==
Manufacturers have sought ways to distinguish their product by supposedly "improving" cubic zirconia. Coating finished cubic zirconia with a film of [[diamond-like carbon]] (DLC) is one such innovation, a process using [[chemical vapor deposition]]. The resulting material is purportedly harder, more lustrous and more like diamond overall. The coating is thought to quench the excess [[Dispersion (optics)#Dispersion in gemology|fire]] of cubic zirconia, while improving its refractive index, thus making it appear more like diamond. Additionally, because of the high percentage of diamond bonds in the amorphous diamond coating, the finished simulant will show a positive diamond signature in [[Raman spectroscopy|Raman spectra]].

Another technique first applied to [[quartz]] and [[topaz]] has also been adapted to cubic zirconia: An [[iridescence|iridescent]] effect created by vacuum-sputtering onto finished stones an extremely thin layer of a precious metal (typically [[gold]]), or certain metal oxides, metal nitrides, or other coatings.<ref>{{cite web |title=Designer enhanced gemstones |publisher=Azotic Coating Technology, Inc. |url=http://azotic.us/gems.php |access-date=3 November 2010|year=2010}}</ref> This material is marketed as "mystic" by many dealers. Unlike diamond-like carbon and other hard synthetic ceramic coatings, the [[iridescence|iridescent]] effect made with precious metal coatings is not durable, due to their extremely low hardness and poor abrasion wear properties, compared to the remarkably durable cubic zirconia substrate.

==Cubic zirconia vis-à-vis diamond==
Key features of cubic zirconia distinguish it from diamond:

[[File:Diamond face trigons scale.jpg|thumb|alt=A triangular facet of a crystal having triangular etch pits with the largest having a base length of about 0.2 mm|One face of an uncut octahedral diamond, showing trigons (of positive and negative relief) formed by natural [[Chemical milling|chemical etching]]]]

*Hardness: cubic zirconia has a rating of approximately 8 on [[Mohs scale of mineral hardness|Mohs hardness scale]] vs. a rating of 10 for diamond.<ref name="Mohs' Hardness of Abrasives"/> This may cause dull and rounded edges in CZ facets; the edges of diamond facets are much sharper by comparison. Furthermore, diamond rarely shows polish marks, and those which are apparent are oriented in different directions on adjoining facets, whereas CZ  shows marks in the same direction of the polish throughout.<ref name=":2" />
*The [[Specific gravity]]  or density of cubic zirconia is approximately 1.7 times that of diamond. This allows gemologists to differentiate the two substances by weight alone. This property can also be exploited, for example, by dropping the stones in a heavy liquid and comparing their relative rates of descent: diamond will sink more slowly than CZ.<ref name=":2" />
*[[Refractive index]]: cubic zirconia has a refractive index of 2.15–2.18, compared to a diamond's 2.42. This has led to the development of other immersion techniques for identification. In these methods, stones with refractive indices higher than that of the liquid used will have dark borders around the girdle and light facet edges whereas those with indices lower than the liquid will have light borders around the girdle and dark facet junctions.<ref name=":2" />
*[[dispersion (optics)|Dispersion]] is very high at 0.058–0.066, exceeding a diamond's 0.044.
*Cut: Cubic zirconia gemstones can be cut differently than diamonds: The facet edges can be rounded or "smooth".
*Color: only the rarest of diamonds are truly colorless, most having a tinge of yellow or brown to some extent. A cubic zirconia is often entirely colorless: equivalent to a perfect "D" on [[Diamond color|diamond's color]] grading scale. That said, desirable colors of cubic zirconia can be produced including near colorless, yellow, pink, purple, green, and even multicolored.
* Thermal conductivity: Cubic zirconia is a thermal insulator whereas diamond is the most powerful{{Citation needed|date=May 2024}} thermal conductor. This provides the basis for Wenckus’ canonical identification method, the industry standard.<ref name=":1" />

=== Effects on the diamond market ===
Cubic zirconia, as a [[diamond simulant]] and jewel competitor, can potentially reduce demand for [[conflict diamonds]], and impact the controversy surrounding the rarity and value of diamonds.<ref name=":3">{{Cite web|url=https://priceonomics.com/post/45768546804/diamonds-are-bullshit|title=Diamonds Are Bullshit|last=Dhar|first=Robin|date=19 March 2013|website=Priceonomics|access-date=10 May 2018|archive-date=11 April 2018|archive-url=https://web.archive.org/web/20180411194706/https://priceonomics.com/post/45768546804/diamonds-are-bullshit|url-status=dead}}</ref><ref name=":4">{{Cite web|url=https://www.forbes.com/sites/quora/2017/07/03/why-smart-people-buy-cubic-zirconia-engagement-rings/#70ca7ca7594f|title=Why Smart People Buy Cubic Zirconia Engagement Rings|last=Muller|first=Richard|date=3 July 2017|website=Forbes}}</ref>

Regarding value, the paradigm that diamonds are costly due to their rarity and visual beauty has been replaced by an artificial rarity<ref name=":3" /><ref name=":4" /> attributed to price-fixing practices of [[De Beers|De Beers Company]] which held a monopoly on the market from the 1870s to early 2000s.<ref name=":3" /><ref name=":5">{{Cite news|url=https://www.economist.com/node/2921462|title=The Diamond Cartel|last1=Johannesburg|last2=Windhoek|date=15 July 2004|newspaper=The Economist}}</ref> The company pleaded guilty to these charges in an Ohio court in 13 July 2004.<ref name=":5" /> However, while De Beers has less market power, the price of diamonds continues to increase due to the demand in emerging markets such as India and China.<ref name=":3" /> The emergence of artificial stones such as cubic zirconia with optic properties similar to diamonds, could be an alternative for jewelry buyers given their lower price and noncontroversial history.

An issue closely related to monopoly is the emergence of conflict diamonds. The [[Kimberley Process Certification Scheme|Kimberley Process]] (KP) was established to deter the illicit trade of diamonds that fund civil wars in [[Angola]] and [[Sierra Leone]].<ref name=":6">{{Cite magazine|url=https://time.com/blood-diamonds/|title=Blood Diamonds|last=Baker|first=Aryn|magazine=Time}}</ref> However, the KP is not as effective in decreasing the number of conflict diamonds reaching the European and American markets. Its definition does not include forced labor conditions or human right violations.<ref name=":6" /><ref>{{Cite web|url=https://www.brilliantearth.com/news/how-to-beat-the-smugglers-and-stop-blood-diamonds/|title=A Simple Way To Stop Blood Diamonds|last=K.|first=Greg|date=2 December 2014|website=Brilliant Earth}}</ref> A 2015 study from the [[Enough Project]], showed that groups in the [[Central African Republic]] have reaped between US$3&nbsp;million and US$6&nbsp;million annually from conflict diamonds.<ref name=":7">{{Cite web|url=http://www.scmp.com/news/world/article/2043572/why-illicit-diamond-trade-almost-gone-not-yet-forgotten|title=Why the illicit diamond trade is (almost) gone, but not yet forgotten|date=21 February 2017|website=SCMP}}</ref> UN reports show that more than US$24&nbsp;million in conflict diamonds have been smuggled since the establishment of the KP.<ref>{{Cite web|url=https://www.reuters.com/article/us-centralafrica-un-panel/gold-diamonds-fuelling-conflict-in-central-african-republic-u-n-panel-idUSKBN0IO21420141105|title=Gold, diamonds fuelling conflict in Central African Republic: U.N. panel|last=Flynn|first=Daniel|date=5 November 2014|website=Reuters}}</ref> Diamond simulants have become an alternative to boycott the funding of unethical practices.<ref name=":7" /> Terms such as “Eco-friendly Jewelry” define them as conflict free origin and environmentally sustainable.<ref>{{Cite web|url=https://www.brides.com/gallery/moissanite-engagement-rings|title=15 Moissanite Engagement Rings for the Eco-Friendly Bride|last=Hoffower|first=Hillary|date=21 April 2018|website=Brides}}</ref> However, concerns from mining countries such as the [[Democratic Republic of the Congo|Democratic Republic of Congo]] are that a boycott in purchases of diamonds would only worsen their economy. According to the Ministry of Mines in Congo, 10% of its population relies on the income from diamonds.<ref name=":6" /> Therefore, cubic zirconia are a short term alternative to reduce conflict but a long term solution would be to establish a more rigorous system of identifying the origin of these stones.

==See also==
*[[Diamond]]
*[[Diamond simulant]]
*[[Shelby Gem Factory]]
*[[Synthetic diamond]]
*[[Yttria-stabilized zirconia]]

==References==
{{Reflist|refs=
<ref name= Bayanova>{{cite journal|author=Bayanova, T.B.|doi=10.1134/S0869591106020032|title=Baddeleyite: A promising geochronometer for alkaline and basic magmatism|year=2006|journal=Petrology|volume=14|issue=2|pages=187–200|bibcode=2006Petro..14..187B |s2cid=129079168}}</ref>

<ref name=chudoba>{{cite journal|author1=Stackelberg, M. von  |author2=Chudoba, K.|year= 1937|title= Dichte und Struktur des Zirkons; II|journal=Zeitschrift für Kristallographie|volume=97|issue=1–6 |pages=252–262|doi=10.1524/zkri.1937.97.1.252 |s2cid=202046689 }}</ref>

<ref name=growth>{{cite book |doi=10.1007/978-3-540-74761-1_14 |chapter=Synthesis of Refractory Materials by Skull Melting Technique |title=Springer Handbook of Crystal Growth |date=2010 |last1=Osiko |first1=Vyacheslav V. |last2=Borik |first2=Mikhail A. |last3=Lomonova |first3=Elena E. |pages=433–477 |isbn=978-3-540-74182-4 }}</ref>

<ref name=Hesse>{{cite book|author=Hesse, Rayner W. |title=Jewelrymaking Through History: An Encyclopedia|url=https://books.google.com/books?id=DIWEi5Hg93gC&pg=PA72|publisher=Greenwood Publishing Group|isbn=978-0-313-33507-5|page=72|year=2007}}</ref>

}}

==Further reading==
*{{cite book
| last = Nassau
| first = Kurt
| year = 1980
| title = Gems Made by Man
| publisher = Chilton Book Company
| isbn = 0-8019-6773-2}}
{{Authority control}}

{{DEFAULTSORT:Cubic Zirconia}}
[[Category:Crystals]]
[[Category:Diamond simulants]]
[[Category:Gemstones]]
[[Category:Refractory materials]]
[[Category:Synthetic minerals]]
[[Category:Zirconium dioxide]]
[[Category:Fluorite crystal structure]]

[[fr:Zircone]]