“... Warm Springs: Thundereggs occurs in many areas of the Warm Springs Indian reservation in Central Oregon. Collecting is strictly forbidden except for members of the Warm Springs tribe who live there. There are several locations within this area, such as Mutton Mountain, Big Oak Springs, Hunt Ranch and also the Frieda location, which is just to the north of the reservation boundary. The Mutton Mountain eggs could easily be mistaken for Priday eggs, except that the matrix usually has more shades of grey. The agate cores can be waterline or fortification in pale shades. The Big Oak Springs and Hunt Ranch eggs are massive and are usually found as chunks broken from a larger mass of rhyolite. The agate cores are dark blue to black with many containing tube formations.The Frieda eggs contain clear to bluish waterline and fortification agate, with a small percentage containing the most desirable green tube formations, which are coated with chromite. Many times the agate filling of the Frieda eggs is incomplete, with stalactities and stalagmites within the cavity....”

From a personal Notice from Mark Ketsdever, Hillsboro, Oregon, 2011