The Sangre de Cristo Mountains of south-central Colorado are a classic example of a fault-block mountain range. They are an uplifted chain of rugged peaks consisting of ancient Precambrian basement rock and younger Pennsylvanian-Permian sedimentary rocks. The Precambrian rocks include truly ancient metamorphic country rock and slightly younger granites. Throughout most of its length, the crest of the range is capped by a thick sequence of tilted Pennsylvanian-Permian red beds. These striking red-colored sediments take on a distinctive ruddy hue during certain times of the day, thus the name Sangre de Cristo ("Blood of Christ"). The eastern slopes of the Sangres are also made up of these tilted Pennsylvanian-Permian sediments. On the western side of the Sangres, Precambrian granite is exposed along the base of the range. Higher up the slopes, younger Paleozoic sediments lie unconformably upon the ancient Precambrian basement rock. In some sections of the Sangre de Cristos, Precambrian granite forms the crest of the range. Examples include the Mount Blanca complex and the Culebra Peak area.
The Sangre de Cristo Mountains were pushed up along a set of high-angle thrust faults that pretty much run the length of the chain. Faulting was initiated during Laramide times, but sporadic movement occurred throughout the Tertiary Period.
Culebra Peak rises up along the crest of the Sangre de Cristos, less than 9 miles from the New Mexico border. The peak is located near the contact between ancient Precambrian country rock and younger Pennsylvanian sediments. Most of the peaks in the Culebra Range are made up of this Precambrian granite. Only on the eastern side of the range do younger Pennsylvanian-Permian sediments crop out.
No mining districts occur in the Culebra Range. The nearest gold-producing districts are in the Spanish Peaks area, some 20 miles to the northeast. The Spanish Peaks are home to three small mining districts: the La Veta District, the Spanish Peaks District, and the Wayatoya Creek District. The first was founded on lode gold production while the last two were centered on placer gold production. The La Veta District contained small veins of gold-bearing sulfides emplaced within a Tertiary intrusion.
The Culebra Range forms the southernmost part of the Sangre de Cristo mountain chain in Colorado. The Culebras (which means "snake" in Spanish) consist of several high peaks that rise up just north of the New Mexico border. The Culebra Range presents quite a challenge to the prospector. The area of interest is extensive, remote, and extremely rugged. In addition, the Culebra Range is not known for its mineral deposits. Although the geology is favorable, very few ore bodies have been discovered in the area. Finally, access to Culebra Peak is restricted. Permission is required to enter the area.
Prospectors will probably want to concentrate on the Precambrian crystalline rocks that make up most of Culebra Peak and the surrounding mountains. This area includes Vermejo Peak, Purgatoire Peak, Red Mountain, and Miranda Peak. The fault that cuts across the range just south of Purgatoire Peak and the north-south trending fault that intersects it also merit attention. The north-south fault runs along the eastern edge of the range, close to the Las Animas County and Costilla County line. One or both of these faults may have served as a conduit for ore-bearing solutions.
Prospectors may want to focus their search on areas conducive to the concealment of a mine portal and the tailings associated with it. The hidden mine shaft is said to be quite extensive. There should be a correspondingly large amount of waste rock and tailings. Heavily forested mountain slopes, brush-choked ravines, and landslide deposits would be likely candidates for concealment. An organized and detailed reconnaissance of the area is probably in order. This should include a meticulous search for metal-bearing float in the canyons and streams that cut through the area. A metal-detector would certainly be useful in the search.