Editing Sapphire (section)

===Color-change sapphire===
A rare variety of natural sapphire, known as color-change sapphire, exhibits different colors in different light. Color change sapphires are blue in outdoor light and purple under [[incandescent]] indoor light, or green to gray-green in daylight and pink to reddish-violet in incandescent light.{{clarification needed|reason=incandescent light used twice to refer to different color states|date=August 2024}} Color-change sapphires come from a variety of locations, including [[Madagascar]], [[Myanmar]], [[Sri Lanka]] and [[Tanzania]]. Two types exist. The first features the [[chromium]] chromophore that creates the red color of ruby, combined with the [[iron]] + [[titanium]] chromophore that produces the blue color in sapphire. A rarer type, which comes from the Mogok area of Myanmar, features a [[vanadium]] chromophore, the same as is present in Verneuil synthetic color-change sapphire.

Virtually all gemstones that show the "alexandrite effect" (color change or '[[Metamerism (color)|metamerism]]') show similar absorption/transmission features in the visible spectrum. This is an absorption band in the yellow (~590&nbsp;nm), along with valleys of transmission in the blue-green and red. Thus the color one sees depends on the spectral composition of the light source. Daylight is relatively balanced in its spectral power distribution (SPD) and since the human eye is most sensitive to green light, the balance is tipped to the green side. However incandescent light (including candle light) is heavily tilted to the red end of the spectrum, thus tipping the balance to red.<ref>{{cite journal| title=Gemstones with alexandrite effect| url=https://www.gia.edu/doc/Gemstones-with-Alexandrite-Effect.pdf| date=Winter 1982| first1=E.| last1=Gübelin| first2=K.| last2=Schmetzer| volume=18| issue=4| journal=Gems & Gemology| pages=197–203| doi=10.5741/GEMS.18.4.197| bibcode=1982GemG...18..197G| access-date=5 November 2019| archive-date=5 November 2019| archive-url=https://web.archive.org/web/20191105010509/https://www.gia.edu/doc/Gemstones-with-Alexandrite-Effect.pdf| url-status=live}}</ref>

Color-change sapphires colored by the Cr + Fe/Ti chromophores generally change from blue or violet-blue to violet or purple. Those colored by the V chromophore can show a more pronounced change, moving from blue-green to purple.

Certain synthetic color-change sapphires have a similar color change to the natural gemstone [[alexandrite]] and they are sometimes marketed as "alexandrium" or "synthetic alexandrite". However, the latter term is a misnomer: synthetic color-change sapphires are, technically, not synthetic alexandrites but rather alexandrite ''simulants''. This is because genuine alexandrite is a variety of [[chrysoberyl]]: not sapphire, but an entirely different mineral from corundum.<ref name="Weldon-2013">{{cite web| title=An Introduction to Synthetic Gem Materials| url=http://www.gia.edu/gem-synthetic| last=Weldon| first=Robert| work=GIA| publisher=Gemological Institute of America Inc.| access-date=14 August 2014| archive-date=12 November 2013| archive-url=https://web.archive.org/web/20131112191736/http://www.gia.edu/gem-synthetic| url-status=live}}</ref>