Mexican Thundereggs from the proximity of Cumbres de Majalca in Chihuahua are called “Redskin Geodes”. They are showing a brick-red outer skin. Usually they are bearing in their center beautiful crystalline quartz and only very seldom banded agate. The specimen shown here is representing the exception.
Brad Cross is mentioning this location in his monography “The agates of northern Mexcio” on page 112.