These agates are originated on the Rancho Colorado in the Cerros las Borrogas in the proximity of Nuevas Casas Grandes. Interestingly enough (unfortunately) nodules of this discovery site lead to more than 60% black to brown Siderite in their center ("Dudes"). If solid agate in the nodule is to be found, this material will be coloured often in pastels and only rarely in intensively tones. The colours are yellowish, brownish and violet. The formation of small white balls in the layers of the agate is interesting. Similarities point themselves thereby and through similar colours to the Parcelas agates.
More informations about the locality and the agate-formation is given by Brad L. Cross in his book “The Agates of Northern Mexico”, page 65.