The Marfa agates have been found  at several ranches and along the roadcuts south of Marfa, Texas for several decades and they still can be found today due to erosion. Those agates tend to be colorless to white "Waterline" types, and they appear to have been weathered out of the basalt beds atop the white ash layers. Since grassy Big Bend of Texas is prime for raising cattle, much of the land are fenced and made private and anyone are strongly discouraged to cross the fences into the private lands due to the safety concerns for the cattle (expensive to manage!) and there are some rumors of armed ranchers willing to use you as "target practices" (actually happened in New Mexico).       Even the agates from Marfa were known for several decades, the agates with strong blue to black colors have recently emerged from the private lands, and I can't recall any other agates outside the Big Bend of Texas coming with such strong color combination of black, white and blue. I was able to obtain some by trading with a Marfa jeweler who has a special permission to collect on the private ranches in exchange for producing lapidary jewelry for the ranch owners. What makes those agates even more special is that some agates contain what may be most colorful plume structures in any agates around the world. The plumes in the agates are typically black, but the pink, red, orange, yellow, green and even blue plumes have been found. Some plume agates can contain the combo of different colors, earning their nickname: "Marfa Banquet" Agate.

YOU CAN CLICK ON THE PICTURES TO SEE LARGER PICTURES Rough Appearance: Varies from clear see-through nodules to dark irregular shaped nodules with black, brown or white skins
Mostly clear to white, sometimes come in blue to black color combos, can be confused with similar looking Balmorhea Agates