Sapphire
A durable gemstone prized for its blue and fancy colors.
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Sapphire is a precious gemstone variety of the mineral corundum, composed of aluminium oxide with trace elements.[1] Red corundum stones are called rubies rather than sapphires, while pink corundum may be classified as either depending on locale.[2] The Latin and Greek word "sappheiros," which originally referred to lapis lazuli, is the source of the modern name "sapphire."[1]
Key facts and history
Sapphire is a variety of corundum, and any corundum that is not red qualifies as sapphire.[3] The intense blue color of sapphire is caused by the addition of titanium and iron to corundum.[4] Blue sapphire's color results from a charge transfer process between Fe²⁺ and Ti⁴⁺ ions.[4] Only 0.01% of titanium and iron is needed to produce a blue color in sapphire.[4]
The sapphire deposits of Kashmir are well known for their superior vivid blue hue, described as "blue velvet".[5] Sapphire deposits are located in Australia, Afghanistan, Cambodia, Cameroon, China, Colombia, Ethiopia, India, Kenya, Laos, Madagascar, Malawi, Mozambique, Myanmar, Nigeria, Rwanda, Sri Lanka, Tanzania, Thailand, the United States, and Vietnam.[6] To improve color and clarity, sapphires undergo heat treatment in furnaces at temperatures ranging from 800 to 1800 °C.[7] The practice of heating gemstones has been documented as far back as the Roman era.[8]
What the research sources say
The "Blue Sapphire" account from Causes of Color states that sapphire has been prized since its use in Chinese axes dating to around 4000 B.C..[4] The same source notes that Australia is a dominant producer of sapphires, but these stones are considered less valuable due to their very dark color.[4] According to the GIA, when trace elements are iron and titanium, the corundum is blue sapphire.[9] The GIA also reports that chromium can cause the red color of ruby or the pink of pink sapphire.[9]
The same source states that many synthetic sapphires are still made by flame fusion, and flux-grown sapphires have been available since the 1960s.[10]
References
- Wikipedia, "Sapphire" (CC BY-SA 4.0), which cites: "Greek Word Study Tool", www.perseus.tufts.edu (original not read by us) en.wikipedia.org
- Wikipedia, "Sapphire" (CC BY-SA 4.0), which cites: "Sapphire", GIA (we also read that source) en.wikipedia.org
- "Sapphire", GIA. facts only, no text reused. gia.edu
- "Blue Sapphire", Causes of Color. facts only, no text reused. webexhibits.org
- Wikipedia, "Sapphire" (CC BY-SA 4.0), which cites: Hughes, "Ruby & Sapphire: A Gemologist's Guide", RWH Publishing/Lotus Publishing, 2017; "History of Kashmir Sapphires", 13 September 2019 (we also read that source) en.wikipedia.org
- Wikipedia, "Sapphire" (CC BY-SA 4.0), which cites: Hughes, "Ruby & Sapphire: A Gemologist's Guide", RWH Publishing/Lotus Publishing, 2017 (we also read that source) en.wikipedia.org
- Wikipedia, "Sapphire" (CC BY-SA 4.0), which cites: Research Laboratory, "Identification of heated / unheated status on ruby and sapphire", Gemmological Association of All Japan Co., Ltd., 2007 (original not read by us) en.wikipedia.org
- Wikipedia, "Sapphire" (CC BY-SA 4.0), which cites: Nassau, "Gemstone Enhancement", Butterworths, 1984, p. 95 (original not read by us) en.wikipedia.org
- "Sapphire Description", GIA. facts only, no text reused. gia.edu
- Weldon, "An Introduction to Synthetic Gem Materials", GIA. facts only, no text reused. gia.edu
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Sapphire (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Sapphire (CC BY-SA 4.0).
- Word definitions: the , each quoted from its Wikipedia article.
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