Quartz

specimen number:
2292334

location:
Black Dome, British Columbia, Canada

description:
An attractive matching pair of cut and polished thunder egg agate.

Black Dome Mountain, located in south-central British Columbia, Canada, is a volcanic complex composed of Eocene to Pliocene volcanic rocks, including andesite, rhyolite, and basalt. Historically, the area gained attention after the 1947 discovery of gold and silver-bearing epithermal quartz veins, which led to commercial mining operations starting in the 1980s. Geologically, the region is also recognized for its volcanic glass deposits, such as perlite and obsidian, which host distinct nodular formations.

Thundereggs, scientifically known as lithophysae, form within silica-rich volcanic lava flows, particularly rhyolite and volcanic ash. As the viscous lava cools, trapped gases expand to form spherical or star-shaped cavities within the rock matrix. Over millions of years, silica-bearing groundwater or hydrothermal fluids seep into these hollow spaces through microscopic fractures, slowly depositing layers of chalcedony, agate, jasper, or quartz crystals that fill the interior voids.

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