Very Fine Mexican Jelly Opal—The National Gemstone of Mexico. Magdelena, Jalisco, Mexico © 2002-2010 Bonhams 1793 Ltd
Weighing approximately 8.95 carats and measuring 18.0 x 13.0 x 8.0 mm - Sold for $8,540
Opals were formed during the Cretaceous period and brought to the Earth's surface during the Pleistocene age. There are 25 or so varieties of opals but the most significant fire opal deposits are found in Mexico. One of the two largest sites for mining the Mexican fire opal, is located near Magdalena, Jalisco, a small city located approximately 100 miles east of Vallarta. Magdalena is in a region laden with igneous rocks, obsidian, volcanic lava, and more than 300 opal mines.
Mexican fire opals consist of silicon dioxide or silica spheres arranged in an orderly pattern with iron oxide dispersed throughout giving the fire opal its distinctive brilliant flame-like colors of yellow, orange, and red. The three most important attributes of the fire opal are body colors, transparency, and play-of-color (differing colors when viewed from various angles). Simply put, the greater the play-of-color, the more precious the gemstone. Because most opals are not faceted, they are generally displayed in the cabochon form; however, fire opals are often the exception.
Mexican fire opal was known by the Aztecs and was used by Mayans as well for ritualistic purposes and in various mosaics. Even today many connoisseurs believe that fire opals bestow courage, stamina, and energy to the wearer due to its warm, fiery orange-red colors. The present is oval-cut exceptional example of a jelly opal from this famed region of Mexico with its broad flashes of yellow, orange and green. This is a true gem for the collector of precious fire opals
Bonhams & Butterfields. The Nature of Opals, 10 Nov 2010. 220 San Bruno Avenue, San Francisco www.bonhams.com