Opal-AN

specimen number:
4991037

location:
Kopasz Hill quarry, Tarcal, Tokaj, Borsod-Abauj-Zemplen Co., Hungary

description:
Glassy colorless bubbly opal across matrix. Brightly fluorescent as shown in the photo. The video shows the sample in normal daylight. In great condition.

The Kopasz Hill quarry near Tarcal, situated in the Tokaj Mountains of Borsod-Abauj-Zemplen County, Hungary, is an active or intermittently operated commercial andesite aggregate quarry where intensive mineral collecting phases peaked around 2013 to 2015 before access was officially closed to collectors. Geologically, the site is defined by Miocene calc-alkaline volcanic formations, where andesite and related volcanic rocks contain hydrothermal alteration zones, veins, and cavities that host secondary silica deposition.

The quarry became globally famous among mineral enthusiasts for exceptional water-clear hyalite, a form of opal-AN, which coats fracture zones and mineral surfaces. Under shortwave (SW) ultraviolet light, this hyalite opal exhibits a brilliant and intense neon green fluorescence, frequently accompanied by associated minor calcite or aragonite that display contrasting yellow or bluish responses under longer UV wavelengths.

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