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Smithsonian National Museum of Natural History

Opal (var. hyalite)

No description of this
                                          asset is available
Photo by Ken Larsen. Click to zoom.
Catalog Number NMNH G11521-00
Locality Jalisco, Mexico
Weight 3.45 ct

A rather remarkable hyalite opal found in 2013 in Zacatecas, Mexico is “daylight fluorescent,” meaning that it will fluoresce under regular daylight conditions, no ultraviolet light (long wave or short wave) needed.  This opal typically occurs as botryoidal masses on the matrix rock. As the opal commonly forms in thin layers, gemstones have been difficult to fashion. Faceting a gem larger than a carat is unusual. This opal ranges from near colorless to a light to medium yellow under incandescent light and an almost neon yellowish-green to greenish-yellow under fluorescent or daylight conditions. This triangular cut opal is 3.54ct and is transparent with a yellowish-green color. Under ultraviolet light it glows an intense yellow-green.



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