Cold Mountain Thundereggs are similar to Butterfly Jasper but offer a brighter range of colors. Also the thundereggs can contain water banding and features red, mauve, or black “webbing.” While technically a rhyolite due to its thunderegg nature, Cold Mountain Thundereggs are highly silicate and filled brecciation. This material takes an exceptional polish which makes it ideal for both cabochons and specimens. The rough nodules usually have a bumpy exterior, but occasionally can be smooth. Nodule sizes can run from 2 inches to 8 inches, with the average size ranging between 3 – 4 inches.
Pictured wet in the first image