Moctezuma agates were collected in an area approximately 15 miles east of Estación Moctezuma on the ranches San Martin and El Barreal. Those agates are surface findings with an average size from one to two inches ( the big ones are having an diameter up to 3 inches). The with skin is caused by wheathering and is typically for this type of agate. Today nice collectors items are difficult to obtain - in the earlier days (up to 1980) those agates were marketed in big quantities.
These agates are easily distinguished by their white skin. The pattern is showing pastels such as shades of pink, salmon, yellow, grey and white in the core. Greyish to bluish translucent chalcedony is representing the outer rim. In this zone a very fine and nearly transparent white banding may occur. It is giving an etherical apperance to the agate.
More informations about the locality and the agate-formation is given by Brad L. Cross in his book “The Agates of Northern Mexico”, page 83 - 85.