2.55" Botryoidal Hyalite Opal with Chalcedony - Mexico

This 2.55" wide specimen features an association of glassy botryoidal hyalite opal and chalcedony, collected from San Luis Potosi, Mexico. Portions of this specimen exhibit green fluorescence under shortwave UV light. The reaction to shortwave UV is a result of trace uranyl ions.

Hyalite is a transparent to translucent variety of opal that typically bears a globular structure. An amorphous form of silica (SiO2), hyalite opal forms as a volcanic sublimate in volcanic or pegmatic rock and is thereby considered a mineraloid. It can be referred to as water opal, jalite, or even Muller's glass, named after the man who discovered it, Franz-Joseph Müller von Reichenstein. It has a hardness of 5.5–6 on the Mohs scale and exhibits conchoidal fracturing.
Opal var. Hyalite & Quartz var. Chalcedony
San Luis Potosi, Mexico
2.55 x 1.25"