By Marc Wilson
Pictured above, the mineral hyalite is a type of non-precious opal that is usually formed in hot springs environments, like
Yellowstone National Park.
Hyalite often contains traces of uranium as impurities. When there is just the right amount of uranium in the hyalite, it causes it to fluoresce brilliant yellow-green under ultraviolet radiation, more commonly called “black light.”
Most fluorescent hyalite reacts best to the shorter wavelengths of ultraviolet but this specimen has an intense reaction to long wave ultraviolet. This is good for us because short wave ultraviolet is completely filtered out by glass or plastic, but long wave can penetrate through both allowing us to cause it to fluoresce with a UV laser pointer.
This remarkably fluorescent hyalite opal was discovered in Zacatecas, Mexico in 2013. It came from a very small deposit that is now completely worked out. We are very fortunate to have such stunning examples
from this unusual occurrence.
Marc Wilson is the head of the Minerals Section at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
