The agates from the region of Nipomo in San Luis Obispo County are famous for the beautiful pseudomorphic formations they are showing. These are usually pointed, tufted aggregates which trace the form of previously existing minerals.

About the rarity of these agates, already the autor Lelande Quick wrote in his "book of agates" from the year 1963. Due to their beautiful agates and its excellent climate, this region was one of his favorite rockhounding areas. The agates occur on bean fields, where they have been no rarity until the 1940ies and 1950ies when most of them were collected by rockhounds. Also only a few farmers allowed the collecting of agates on their fields in the 1960ies .

A second variety of agate, which contains no Pseudomorphs, but still the primeval mineral - shiny golden aggregates of Marcasite - nowadays still once in a while goes on sale.