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CMT149 Cold Mountain Thunderegg Specimen


This polished specimen displays reddish brown, mauve, and black coloring with translucent, blue-grey chalcedony filling in the thunderegg fracture pattern.

6" x 3.5" x 2.25"
1 lb 15.8 oz

Cold Mountain Thundereggs are from the Sierra Mountains in Mexico. The thundereggs can contain water banding and feature red, mauve, or black “webbing.” While technically a rhyolite due to its thunderegg nature, Cold Mountain Thundereggs are highly silicate and feature large amounts of brecciation that has also been filled with silica, so this material takes an exceptional polish, making it ideal for both cabochons and specimens.