Mineraloid variety ✺ Glows under UV

Hyalite

Variety of Opal.

📜 Key facts

Origin & sources	Valeč (Czech Republic), Zacatecas (Mexico), Spruce Pine (North Carolina, USA) and many volcanic regions.
Composition	Clear, glassy opal (hydrated silica, SiO₂·nH₂O) with trace uranium

Mineral data: see Opal.

Longwave UV (~365 nm)	Green
Shortwave UV (~254 nm)	Intense green

Water-clear and easy to overlook in daylight, hyalite glows a vivid green because of trace uranyl ions. That glow is how it is told apart from glass.

Reactions vary by locality and specimen; many specimens of a fluorescent species do not glow. Shortwave UV can burn skin and damage eyes. Wear UV-blocking glasses, and never look into any UV lamp. Sources: Wikipedia: Hyalite · Franklin Mineral Museum fluorescent mineral checklist. More UV-reactive stones →