Casas Grandes, Parcelas and Calandria agates appear to be so similar that they can be confused with each other. It's typical to find Casas Grandes agates that are white to gray with snowy/fuzzy dots in them. Some agates come with the pink, blue, lavender, yellow, orange and purple colors. What may distinguish the Casas Grandes Agates from the Parcelas Agates is that the Casas Grandes Agates look rusty (yellowish) while Parcelas Agates  have reddish dark skins. Those agates are some of few oldest agates mined in Northern Mexico (1955), but ever since, there had been some sparse mining of those agates due the difficulty of obtaining the agates out of hard andesite bedrocks as well as the fact that about 75% of the nodules contain nothing but siberite (brown "calcite").  I can't help but wonder if Casas grandes and Calandria agates share similar sources since the Calandria agates seem to come from a placer deposit. .
YOU CAN CLICK ON THE PICTURES TO SEE LARGER PICTURES Rough Appearance: Rusted look, pitted surface
Can be confused with Parcelas Agates.