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“...The very rare Tranquillon Peak thundereggs are originated from Vandenberg Air Force Base near Lompoc. Collecting is not allowed except for a few special occasions in the past. Many of the eggs collected have no agate in the cores, making any with agate that much more valuable. It is doubtful that more than a couple dozen specimens exist worldwide. The eggs are in a rhyolite mass that intruded marine sediments, so they contain disseminated marcasite and smell like sulphur when dry sanded. On rare occasions, these eggs are found on the westernmost section of Jalama Beach as waterworn pebbles, not even resembling the thundereggs that they are....”

written by Mark Ketsdever, Hillsboro, OR