COYAMITO AGATES

Among the Finest Agates of Northern Mexico

Coyamito agate is widely considered one of the finest agates produced in the Sierra del Gallego region of Chihuahua, Mexico. Known for its vivid colors and unusual internal structures, this locality has produced some of the most visually striking agates ever discovered in Mexico.

Coyamito agates often display brilliant shades of red, orange, yellow, and purple, sometimes appearing together in rare color combinations such as purple and yellow, rose and white, or mustard and red. These vivid contrasts give Coyamito agates a distinctive and highly collectible appearance.

Many Coyamito nodules are partially hollow and contain internal structures that can form remarkable patterns when cut. In some cases, cylindrical tubes run through the center of the agate. When sliced perpendicular to these tubes, the resulting cross-section reveals concentric rings that create dramatic “eye” patterns.

The Coyamito deposits are located on Rancho Coyamito Norte in the Sierra del Gallego area of Chihuahua. Agate was first discovered there in the early 1940s by Dave and Lucille Harris of El Paso. In 1948, Ramón Peña filed the first commercial mining claim at the ranch and worked the deposit for Manuel Ontiveros. Over the years several collectors and miners have worked the area, with more recent production associated with ranch owner Marín Carrillo.

Three primary agate-producing deposits occur at Coyamito: Los Alamos, La Fortuna, and La Sonoreña. Each deposit produces agates with distinctive characteristics.

Los Alamos Deposit

The Los Alamos area, also known as “The Poplars,” lies in the southern portion of the ranch and is named after the large trees surrounding a spring that historically served explorers and travelers.

Agates from this area are often found near the creek bed and are known for their dark lavender and yellow banding. Many specimens from this deposit display remarkable pseudomorphs of agate after pseudohexagonally twinned aragonite crystals, producing unusual geometric structures within the stone.

The nodules from Los Alamos range in size from a few inches to more than 12 inches in diameter. Their exterior surfaces are commonly coated with a rust-colored, powdery mineral known as limonite, which gives the nodules a distinctive reddish appearance.

La Fortuna Deposit

Located just a short distance uphill from Los Alamos, the La Fortuna deposit produces agates that differ significantly in size, texture, and banding patterns.

These nodules are generally smaller, typically averaging under 4 inches in diameter, and often display bright bands of red, pink, orange, yellow, tan, and white. Unlike the Los Alamos nodules, La Fortuna specimens usually lack the rough limonite coating and instead have smoother exteriors with small pin-sized pits.

La Sonoreña Deposit

The third major locality, La Sonoreña, lies in the northern portion of the ranch near Rancho Derramadero. The nodules here tend to be smaller, averaging 1 to 4 inches in diameter, but they are widely regarded as producing some of the most colorful agates found at Coyamito.

Agates from La Sonoreña commonly display brilliant combinations of reds, purples, yellows, and oranges. Many specimens also contain striking pseudomorph structures, where agate has replaced earlier crystal formations, creating complex and fascinating internal patterns.

Some of the most spectacular Coyamito specimens combine vivid banding with these pseudomorph formations, producing agates that are prized by collectors around the world.