Editing Sapphire (section)

===Star sapphire===
[[File:The Star of Lanka (5784831032).jpg|left|thumb|The 193.39 carat Star of Lanka star sapphire]]
[[File:+68 Komma Sechs - Karat Sternsafir im Rundmogulschliff - Herrenringfassung - 750 Gelbgold - Russische Goldschmiedemeister - Handarbeit um 1990.jpg|thumb|68 carat star sapphire in round mogul cut - men's ring version - 750 yellow gold - Russian goldsmith - handmade around 1990]]
A ''star sapphire'' is a type of sapphire that exhibits a star-like phenomenon known as [[asterism (gemology)|asterism]]; red stones are known as "star rubies". Star sapphires contain intersecting needle-like [[Inclusion (mineral)|inclusions]] following the underlying [[crystal structure]] that causes the appearance of a six-rayed "star"-shaped pattern when viewed with a single overhead light source. The inclusion is often the mineral [[rutile]], a mineral composed primarily of [[titanium dioxide]].<ref name="Emsley-2001">{{cite book |last=Emsley |first=John |title=Nature's Building Blocks: An A-Z Guide to the Elements |year=2001 |isbn=978-0-19-850341-5|pages=451–53 |publisher=[[Oxford University Press]] |location=Oxford}}</ref> The stones are cut ''[[en cabochon]]'', typically with the center of the star near the top of the dome. Occasionally, twelve-rayed stars are found, typically because two different sets of inclusions are found within the same stone, such as a combination of fine needles of rutile with small platelets of [[hematite]]; the first results in a whitish star and the second results in a golden-colored star. During crystallization, the two types of inclusions become preferentially oriented in different directions within the crystal, thereby forming two six-rayed stars that are superimposed upon each other to form a twelve-rayed star.<ref name="DuToit-2014">{{cite web| title=Twelve-Rayed Star Sapphire of Interest| url=http://www.giathai.net/pdf/12rays_purple_star_sapphire.pdf| last=DuToit| first=Garry| publisher=GIA Laboratory, Bangkok| access-date=14 August 2014| archive-date=28 March 2014| archive-url=https://web.archive.org/web/20140328151558/http://www.giathai.net/pdf/12rays_purple_star_sapphire.pdf| url-status=dead}}</ref> Misshapen stars or 12-rayed stars may also form as a result of [[Crystal twinning|twinning]].
The inclusions can alternatively produce a [[Chatoyancy|cat's eye]] effect if the girdle plane of the cabochon is oriented parallel to the crystal's c-axis rather than perpendicular to it. To get a cat's eye, the planes of exsolved inclusions must be extremely uniform and tightly packed. If the dome is oriented in between these two directions, an off-center star will be visible, offset away from the high point of the dome.<ref name="Hughes-2017"/>{{rp|101}}

At 1404.49 carats, [[The Star of Adam]] is the largest known blue star sapphire. The gem was mined in the city of Ratnapura, southern Sri Lanka.<ref name="Sivaramakrishnan-2016">{{cite news | title = World's largest blue star sapphire 'found in Sri Lanka' | url = https://www.bbc.com/news/world-asia-35226276 | first = P | last = Sivaramakrishnan | date = 4 January 2016 | work = BBC News | publisher = [[BBC]] | access-date = 5 January 2016 | archive-date = 5 January 2016 | archive-url = https://web.archive.org/web/20160105031830/http://www.bbc.com/news/world-asia-35226276 | url-status = live }}</ref> The [[Black Star of Queensland]], the second largest star sapphire in the world, weighs 733 [[carat (unit)|carat]]s.<ref name="Kim-2010">{{cite news| url=http://www.latimes.com/news/local/la-me-blacksapphire5-2010jan05,0,872801.story| title=For some, a sapphire has not been their best friend| access-date=5 January 2010| work=[[Los Angeles Times]]| first=Victoria| last=Kim| date=5 January 2010| archive-date=8 January 2010| archive-url=https://web.archive.org/web/20100108084956/http://www.latimes.com/news/local/la-me-blacksapphire5-2010jan05,0,872801.story| url-status=live}}</ref> The [[Star of India (gem)|Star of India]] mined in Sri Lanka and weighing 563.4 carats is thought to be the third-largest star sapphire, and is currently on display at the [[American Museum of Natural History]] in [[New York City]]. The 182-carat [[Star of Bombay]], mined in Sri Lanka and located in the [[National Museum of Natural History]] in [[Washington, D.C.]], is another example of a large blue star sapphire. The value of a star sapphire depends not only on the weight of the stone, but also the body color, visibility, and intensity of the asterism. The color of the stone has more impact on the value than the visibility of the star. Since more transparent stones tend to have better colors, the most expensive star stones are semi-transparent "glass body" stones with vivid colors.<ref name="Hughes-2017"/>{{rp|348–350}}

On 28 July 2021, the world's largest cluster of star sapphires, weighing {{Convert|510|kg|abbr=on}}, was unearthed from Ratnapura, Sri Lanka. This star sapphire cluster was named "[[Serendipity Sapphire]]".<ref>{{Cite web |title=World's largest star sapphire cluster found in backyard |url=https://www.9news.com.au/world/worlds-largest-star-sapphire-cluster-found-in-backyard-in-sri-lanka/1c5b1cc8-fa14-48ac-800c-7516dda154b1 |access-date=28 July 2021 |website=www.9news.com.au |date=28 July 2021 |archive-date=28 July 2021 |archive-url=https://web.archive.org/web/20210728135721/https://www.9news.com.au/world/worlds-largest-star-sapphire-cluster-found-in-backyard-in-sri-lanka/1c5b1cc8-fa14-48ac-800c-7516dda154b1 |url-status=live }}</ref><ref>{{Cite news |last=Salo |first=Jackie |date=27 July 2021 |title=World's largest sapphire cluster worth $100M found in backyard in Sri Lanka |url=https://nypost.com/2021/07/27/worlds-largest-sapphire-cluster-found-in-sri-lankan-yard/ |access-date=28 July 2021 |website=New York Post |language=en-US |archive-date=28 July 2021 |archive-url=https://web.archive.org/web/20210728135726/https://nypost.com/2021/07/27/worlds-largest-sapphire-cluster-found-in-sri-lankan-yard/ |url-status=live }}</ref>