Colorful Agates from the Province of Chihuahua in Mexico (preview)

Agates from the northern Mexican province of Chihuahua are particularly prized by collectors all over the world. Hardly anywhere else is there such a variety of colors and patterns as in the agates found in this mostly barren, desert-like landscape not far from the border with the United States of America, where they have been mined for more than 70 years.

Table of Contents

• Geographical Situation
• Geology of the province of Chihuahua
• Collecting and mining history of northern Mexican agates

The state of Chihuahua (the name means “dry and sandy place” in the indigenous Nahuatl language) is the largest province in Mexico with an area of just under 250,000 km2. It borders New Mexico and Texas (USA) to the north. On the opposite side of El Paso/Texas is the capital of Chihuahua, Ciudad Juárez, which has been in the news again and again in recent years, mainly due to brutal gang crime and intense drug problems.
The majority of the state consists of a desert-like high plateau with sparse vegetation and the Chihuahua Desert in the north, which extends far into the USA. Despite this, almost the entire area of Chihuahua is divided up among just a few landowners, whose ranchos, including sparse grazing areas for their livestock, sometimes cover huge areas. Until a few years ago, the occasional sale of rough agates by the farmers themselves or temporary agreements for agate mining on their land by mostly American-Mexican cooperatives and miners – especially in times of low cattle prices – provided a very welcome additional income.

The main area where the agates presented here were found is in the area between Villa Ahumada and Ojo Laguna; most of the sites are located in the Sierra del Gallego range.

With the exception of the lace agates, which occur in limestones about 180-70 million years old, the northern Mexican agates are all associated with rocks of volcanic origin, which according to CROSS (1996) were formed in the course of volcanic activity about 45-28 million years ago. In the main area of discovery in the Sierra del Gallego, the andesitic rocks (Rancho el Agate-Andesite) consist of numerous different lava flows (KELLER, 1977).
The well-known coconut geodes in the Cerro Mesteño, which in addition to sparkling quartz and calcite crystals often also contain mostly gray-blue agates, however, originate from a gray tuff of the Liebres Formation, which consists of tiny glassy fragments from a former volcanic eruption.
More detailed information on the genesis of northern Mexican agates as well as on the mineralogical, geochemical and geological situation can be found in MROZIK et al. (2023).

According to CROSS (1996), the agates in Chihuahua were first discovered by American collectors (rockhounds) who were able to pick up plenty of colorful agates along Highway 45, which was newly opened in 1945 (connecting the cities of Ciudad Juárez and Ciudad Chihuahua). However, the first mention of northern Mexican agates is already known in a report by the Instituto Geologico de Mexico from 1913.

News of these finds spread quickly in the rockhound clubs in the USA, which were a very popular leisure activity at the time, and soon attracted the first US dealers who, mostly in collaboration with locals, imported large quantities of Mexican rough agate material to the USA until around the mid-1970s. The local middlemen in turn hired helpers (mostly so-called vaqueros = cowboys) who collected the material, which was still abundant on the surface at the time, and handed it over to them for a mostly meagre wage. CROSS (1996) quotes statements by American traders according to which rough agates are said to have been lying on the surface in such large quantities that they could have been shoveled in with an excavator. Gradually, further areas were discovered, which ensured a steady supply of rough agates for almost three decades.

One of the best-known companies involved in the import of Mexican agates at the time was the Southern Gem Mining Company, founded in 1949 by Colonel Elbert Macby Barron, a rather colorful personality. In the early 1960s, for example, he tried to obtain the exclusive rights to sell Laguna agates by making a pact with the landowner at the time and threatening other dealers with legal action for the allegedly illegal sale of Laguna agates. However, financial disputes with the owner of the ranch brought this attempt at a monopoly to a halt after the first shipment of rough agate from Mexico (CROSS, 1996).
Naturally, the surface was soon so heavily searched that the first, generally small-scale mining operations were carried out, working particularly intensively enriched zones with rough agates in the hard Rancho el Agate andesite.
From the mid-1970s to the mid-1990s, only relatively little agate rough from the sites in Chihuahua reached the market, and there were no larger, more significant new finds, although well-known prospectors such as Benny Fenn, well-known from the mineral sector, also made an effort.
The drying up of the agate supply from the Mexican state, which had been producing seemingly inexhaustible rough material for almost a quarter of a century, prompted the best-known American author at the time, June Culp Zeitner, to publish an article entitled “Lament for Laguna” in the most popular US magazine of the time, the Lapidary Journal (1969).