These globular shaped geodes are mined in small pits near the Los Medanos dune field some 60 miles south of El Paso, Texas. Theses nodules are found within a pinkish to white clay-like soil, which represents the altered portion of a dark-colored rhyolithe.
Snowball agates can attain a diameter up to 3 inches. Their skin is white coloured. The inner structure of these nodules is showing very often alternating layers between macroscopic quartz and chalcedony. The colours that snowball agates are showing are pale yellowish to brownish and blue colours. The “pieces de resistance” are balls in red and pink tones.Sagenitic agates (pseudomorphs after tabular crystallizations) are not rare.
“...Snowball agates were called about twenty years ago “Suma-Agates”... “(according to personal report of David Polson)
More informations about the locality and the agate-formation is given by Brad L. Cross in his book “The Agates of Northern Mexico”, page 94 - 96.