{"id":82133,"date":"2016-10-18T01:23:04","date_gmt":"2016-10-18T05:23:04","guid":{"rendered":"https:\/\/www.1stdibs.com\/blogs\/the-study\/?p=82133"},"modified":"2021-12-15T01:01:36","modified_gmt":"2021-12-15T06:01:36","slug":"october-birthstone-opal","status":"publish","type":"post","link":"https:\/\/www.1stdibs.com\/blogs\/the-study\/october-birthstone-opal\/","title":{"rendered":"October Birthstone: Opal"},"content":{"rendered":"
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A 13.5-carat Australian black opal ring with garnets and sapphires<\/a>. Offered by Katherine Jetter<\/p><\/div>\n

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Here is a little riddle for you: the month of October has two birthstones, but only one of them encompasses the colors of other birthstones. If you guessed opal<\/a>, you\u2019re right! <\/span><\/p>\n

Opals are such unusual gemstones that there are too many old-wives tales associated with them, like if you\u2019re a blond, wearing an opal necklace will protect your locks from losing color. Opals were also very fashionable in the early 19th century, up until the publication of Sir Walter Scott\u2019s novel <\/span>Anne of Geierstein<\/span><\/i> in 1829. The title heroine wears an opal and succumbs to an untimely death. However, the British monarchy, and in particular Queen Victoria, did not let this story get in their way, and they frequently gifted opals to friends and family members. October babies should disregard the noise and proudly wear their opals!<\/span><\/p>\n

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Opal and diamond pendant earrings<\/a>. Offered by Dover Jewelry & Diamonds<\/p><\/div>\n

Chemical Composition<\/span><\/h2>\n

Opals are the product of a silicon dioxide and water solution. This dissolved silica substance is pushed through the earth by rainwater and deposited within the cracks of the earth\u2019s strata. Once the water evaporates and the solution hardens, it becomes an opal. Opals fall into two categories: precious\/gemstone variety and common. Precious opals are determined by their play-of-color (the rainbow-like mix of colors that distinguishes the opal from other stones), whereas an opal without radiance is known as common. According to the Gemological Institute of America, \u201c<\/span>play-of-color occurs in precious opal because it\u2019s made up of sub-microscopic spheres stacked in a grid-like pattern \u2014 like layers of Ping-Pong balls in a box. As the light waves travel between the spheres, the waves diffract, or bend. As they bend, they break up into the colors of the rainbow, called spectral colors.\u201d The various hues within the opal are a product of the different colored spheres. <\/span><\/p>\n

There are five types of precious opals: boulder opal, fire opal, crystal\/water opal, black opal, and white\/light opal. Each variety is distinguished by its color. The GIA defines them as following:<\/span><\/p>\n