These polished halves of a Blue Star Thunderegg show brecciated rhyolite filled with translucent agate with pale blue and white feathery banding. It has a few sections of open cavities that reveal sparkling druzy inside, while the opaque rhyolite has patterning similar to petrified wood that radiates outward from the brecciated areas. 

The chalcedony shows green fluorescence under 365nm ultraviolet light.

Polished Surface: 9.2cm x 6.1cm and 9.1cm x 6.2cm
Approx. 1.5" and 2" deep

1lb 7.6oz

Blue Star Thundereggs are a recent find out of Sonora, Mexico. They have a dark grayish to reddish brown outer rind with blue chalcedony inside, typically with a prevalent classic thunderegg star pattern. Many nodules are only partially filled, revealing open inner cavities showing botryoidal formations of chalcedony and crystal druzy inside.