The thunderegg beds of the Calico Mountains near McDermitt, Nevada continue flowing into their siblings beyond the border in Oregon. An allocation is here in the small-scale very difficult. Thundereggs of the Calico Mountains often show a aphanatic (very fine-grained), brownish matrix and usually only bluish-grey and white hues in the central agate. Also their banding is usually rather weak. The occurence of gravitational caused banding is subordinated. With a “lucky cut” they might show a beautiful star shaped pattern.
The website of the virtual Eibonvale Museum is giving more information and is showing several pictures of specimen from this locality.