The Land of Enchantment grows crystals

Pecos diamonds, also referred to as Pecos Valley diamonds, are striking quartz crystals that naturally develop with distinct double terminations. These crystals are found within scattered outcrops of the Permian Seven Rivers Formation, primarily along the Pecos River valley in southeastern New Mexico. While authigenic quartz is commonly present in evaporite deposits across the world and throughout geological history, Pecos Valley diamonds stand out due to their substantial size, diverse coloration, and unique crystal structures.

In addition to quartz, single crystals of dolomite with varying shapes occasionally occur alongside Pecos Valley diamonds, though they are much less widespread. Another mineral, red pseudohexagonal aragonite, is found at a nearby location but has not been observed coexisting within the same rock unit as the diamonds.

The geographical extent of Pecos Valley diamond deposits covers approximately 100 miles in length and up to 25 miles in width along the edges of the Pecos River valley. However, their presence is confined to specific depositional settings that resemble Salinas or salt pans within a broader sabkha environment. Structural features within the quartz indicate that these crystals formed through authigenic processes shortly after the surrounding rock was altered into dolomite. However, their considerable size and the variety of inclusions within them suggest they may have undergone deep burial and formed later through diagenetic processes. Factors such as organic material, dolomite formation, and sulfide oxidation appear to play key roles in the development of Pecos Valley diamonds.