Situated near Ashwood in Jefferson County, Central Oregon, the Alex McDonald Ranch is a renowned destination for rockhounds. The thundereggs at Alex McDonald Ranch formed within rhyolitic volcanic ash layers, characteristic of the region’s Miocene volcanic activity. These formations are similar to those found in nearby areas like Pony Butte and Richardson Ranch, indicating a shared geological history. Thundereggs from this ranch are notable for their unique “Green Eggs & Ham” variety, featuring vibrant green or pink common opal centers. The interiors often display intricate moss patterns and, in some cases, jelly opal that fluoresces under UV light—bright white under longwave and eerie green under shortwave.
Rocks of the Cascades – Thundereggs, Tools & Tradition