This article relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Find sources: "Geuda" – news · newspapers · books · scholar · JSTOR(May 2022)
Geuda (ගෙවුඩ, pronounced gay-yoo-dah[needs IPA]) is a form of the mineral corundum, or sapphire, found primarily in Sri Lanka. Around 70%-80% of gems mined in Sri Lanka belong to geuda varieties. Because of its semitransparent and milky appearance due to rutile inclusions, these stones have little value as gemstones in their natural state.
Geuda was frequently stored in large drums or used to gravel home gardens prior to the 1970s discovery that heat treatment can drastically alter the stone's color.[1]
Some geuda varieties turn to a blue color after heat treatments. Others turn to red after oxidizing. Kowangu pushparaga turns to yellow sapphire after oxidizing. After heating geuda to roughly 1800 °C, the aluminium oxide lattice-work of the gem is disrupted and cooling greatly improves both color and clarity. Though many stones are destroyed by the heating and cooling process, those that survive are significantly altered and rival naturally blue sapphires in both appearance and price.[citation needed]
Referencesedit
^Stephen M Voynick, Yogo: The Great American Sapphire. Mountain Press Publishing Company, Missoula. 1985
This article about a specific mineral or mineraloid is a stub. You can help Wikipedia by expanding it.
geuda, this, article, relies, largely, entirely, single, source, relevant, discussion, found, talk, page, please, help, improve, this, article, introducing, citations, additional, sources, find, sources, news, newspapers, books, scholar, jstor, 2022, pronounce. This article relies largely or entirely on a single source Relevant discussion may be found on the talk page Please help improve this article by introducing citations to additional sources Find sources Geuda news newspapers books scholar JSTOR May 2022 Geuda ග ව ඩ pronounced gay yoo dah needs IPA is a form of the mineral corundum or sapphire found primarily in Sri Lanka Around 70 80 of gems mined in Sri Lanka belong to geuda varieties Because of its semitransparent and milky appearance due to rutile inclusions these stones have little value as gemstones in their natural state Geuda was frequently stored in large drums or used to gravel home gardens prior to the 1970s discovery that heat treatment can drastically alter the stone s color 1 Some geuda varieties turn to a blue color after heat treatments Others turn to red after oxidizing Kowangu pushparaga turns to yellow sapphire after oxidizing After heating geuda to roughly 1800 C the aluminium oxide lattice work of the gem is disrupted and cooling greatly improves both color and clarity Though many stones are destroyed by the heating and cooling process those that survive are significantly altered and rival naturally blue sapphires in both appearance and price citation needed References edit Stephen M Voynick Yogo The Great American Sapphire Mountain Press Publishing Company Missoula 1985 nbsp This article about a specific mineral or mineraloid is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Geuda amp oldid 1173634263, wikipedia, wiki, book, books, library,
