Editing Emerald (section)

=== Treatments ===
Most emeralds are oiled as part of the post-[[lapidary]] process, in order to fill in surface-reaching cracks so that clarity and stability are improved. [[Cedar oil]], having a similar [[refractive index]], is often used in this widely adopted practice. Other liquids, including synthetic oils and polymers with refractive indexes close to that of emeralds, such as ''Opticon'', are also used. The least expensive emeralds are often treated with epoxy resins, which are effective for filling stones with many fractures.<ref>{{Cite journal|date=1991|title=Gems & Gemology|url=https://www.gia.edu/doc/SU91.pdf|journal=Gems & Gemology|volume=XXVII|access-date=19 May 2021|archive-date=19 May 2021|archive-url=https://web.archive.org/web/20210519013713/https://www.gia.edu/doc/SU91.pdf|url-status=live}}</ref><ref>{{Cite journal|date=2001|title=Emerald Treatments|url=https://www.ssef.ch/wp-content/uploads/2018/03/2001_Kiefert_Emerald_treatments.pdf|journal=Kiefert|access-date=19 May 2021|archive-date=19 May 2021|archive-url=https://web.archive.org/web/20210519013714/https://www.ssef.ch/wp-content/uploads/2018/03/2001_Kiefert_Emerald_treatments.pdf|url-status=live}}</ref> These treatments are typically applied in a vacuum chamber under mild heat, to open the pores of the stone and allow the fracture-filling agent to be absorbed more effectively.<ref>Liccini, Mark. [http://www.gemsociety.org/article/emerald-enhancement/ Understanding Emerald Enhancements and Treatments] {{webarchive|url=https://web.archive.org/web/20141221144224/http://www.gemsociety.org/article/emerald-enhancement/ |date=21 December 2014 }}. International Gem Society</ref> The U.S. [[Federal Trade Commission]] requires the disclosure of this treatment when an oil-treated emerald is sold.<ref name=ftc /> The use of oil is traditional and largely accepted by the gem trade, although oil-treated emeralds are worth much less than untreated emeralds of similar quality. Untreated emeralds must also be accompanied by a certificate from a licensed, independent gemology laboratory. Other treatments, for example the use of green-tinted oil, are not acceptable in the trade.<ref>{{cite book|last1=Read|first1=P. G.|title=Gemmology|publisher=Elsevier|isbn=978-1-4831-4467-2|page=180|url=https://books.google.com/books?id=b-7fBAAAQBAJ&q=oil+enhancement+emerald|access-date=30 March 2017|language=en|url-status=live|archive-url=https://web.archive.org/web/20170331024513/https://books.google.com.au/books?id=b-7fBAAAQBAJ&dq=oil+enhancement+emerald&source=gbs_navlinks_s|archive-date=31 March 2017|date=22 October 2013}}</ref> Gems are graded on a four-step scale; ''none'', ''minor'', ''moderate'' and ''highly'' enhanced. These categories reflect levels of enhancement, not ''clarity''. A gem graded ''none'' on the enhancement scale may still exhibit visible inclusions. Laboratories apply these criteria differently. Some gemologists consider the mere presence of oil or polymers to constitute enhancement. Others may ignore traces of oil if the presence of the material does not improve the look of the gemstone.<ref>{{cite book|last1=Matlins|first1=Antoinette Leonard|last2=Bonanno|first2=Antonio C.|title=Jewelry & Gems, the Buying Guide: How to Buy Diamonds, Pearls, Colored Gemstones, Gold & Jewelry with Confidence and Knowledge|publisher=Gemstone Press|isbn=978-0-943763-71-2|page=126|url=https://books.google.com/books?id=WUBWz22wRtEC&q=gemstone+enhancement+traces+of+oil&pg=PA126|access-date=30 March 2017|language=en|url-status=live|archive-url=https://web.archive.org/web/20170330180745/https://books.google.com.au/books?id=WUBWz22wRtEC&pg=PA126&dq=gemstone+enhancement+traces+of+oil&hl=en&sa=X&ved=0ahUKEwj8ruzuuv3SAhUT3mMKHXM_CdwQ6AEILTAD#v=onepage&q=gemstone%20enhancement%20traces%20of%20oil&f=false|archive-date=30 March 2017|year=2009}}</ref>