Thunderegg Agate Slice– Oregon, USA

Thunderegg Agate Slice– Oregon, USA
Dimensions: 6.2 x 5.8 x 1.0 cm

This thunderegg slice features a dramatic deep blue-black chalcedony center surrounded by an earthy brown rhyolite matrix. Fine cream-to-white mineral-filled fractures trace through the host rock, creating a web-like pattern around the chalcedony and emphasizing the contrast between the rugged exterior and polished interior. Small inclusions and subtle orb-like structures are suspended within the dark center, while areas of the chalcedony become beautifully translucent when backlit, glowing in warm amber and smoky tones.

The face has been polished to reveal the interior while the irregular natural edges retain the thunderegg’s original volcanic texture. Thundereggs form when cavities within rhyolitic volcanic rock are gradually filled with silica-rich material, commonly producing agate, chalcedony, and quartz interiors surrounded by their original rhyolite matrix.