I obtained those thundereggs as roughs from a rock shop in Tuscon, Arizona but the location is unknown. They're most likely to be from Mexico. Many thundereggs are filled with white, gray, pink and sometimes red Laguna-like agates often with strong shadowing effect. Many came with sagenite and psuedomorph inclusions.  If anyone recognizes those thundereggs dug in 1970s, please inform me. Thanks!  Pat Mchanan's book has a specimen claimed to be from Fort Cove, Utah but that have not been verified.