There are two Coyamito Ranches in the Sierra del Gallego, Rancho Coyamito Sur and Rancho Coyamito Norte. Only Coyamito Norte is well known for one of the most famous Mexican agates, the Coyamito Agate. It is mined out of the dense Rancho El Agate andesite. Early reports of these agates are from the middle of the 1940s. After the easy picking from the surface small mining efforts with pick and pry bar were started, like the famous La Fortuna Claim. They exactly knew where and how deep they had to dig for agates. Later mining at that place with heavy equipment has been unsuccessful.
Banding of these agates is often not as fine as the best agates from Ojo Laguna. The combination of purple and yellow, a vivid red, orange and blue put them on the top of worldwide agates.
Further informations are given from Brad L. Cross in his book “The Agates of Northern Mexico”, page 44 -46.