Pecos Valley Diamonds

New Mexico's Ancient Attraction

- L.A. BERRY

'AIthough authigenic quartz is relatively common in evaporate sequences, worldwide and throughout geologic history, Pecos Valley diamonds are unique for their large size, variable color, and crystal morphologies." - James L. Albright and Virgil W. Lueth, New Mexico Bureau of Geology and Mineral Resources Or to put it another way, Pecos Valley diamonds are worth the trip.

Okay, with a 7 on the Mohs scale, they're not really diamonds, but New Mexico's colorful, doubly terminated quartz crystals have been casting romantic reflections since their discovery in the Pecos Valley in 1583 by Don Antonio de Espejo, a Spanish miner whose name (aptly enough) meant "mirror."

It's just the kind of story to expect from The Land of Enchantment. New Mexico has been making all the right shortlists: Travel + Leisure's "13 Best US Road Trips," Condé Nast's "14 Reasons We Can't Wait to Travel," National Geographic's "Unforgettable Road Trips" and "Family-Friendly American Road Trips."

SEVEN RIVERS FORMATION: X MARKS THE SPOT

Much like its mineralogical cousin, the Herkimer diamond (quartz), found almost exclusively in central New York, New Mexico’s doubly terminated crystals are choosy about their vugs. Authigenic quartz refers to a mineral that likes to form in place, snugly rolling along through its geochemical millennia.

Pecos diamonds prefer the Seven Rivers Formation, dating roughly 260 million years to the Guadalupian Epoch of the Permian period, when a nearly billion-year-old geologic feature known as the Permian Basin formed amid the eruption of Precambrian tectonics and composed much of southeast New Mexico into west Texas and south to Mexico.