The Great Dikes of the Spanish Peaks
and Silver Mountain

The Great Dikes were formed during the same period of volcanic activity as the Spanish Peaks, Mt. Mestas and Silver Mountain. At the time these vertical granite formations were formed by molten rock, they were located several thousand feet underground, below and among many layers of sedimentary rock. Over time, as the ground rose and the softer rock was eroded away, these igneous intrusions were exposed.

There are essentially three different sets of dikes in the area. One set emanates radially around the West Spanish Peak. The second set emanates radially around Silver Mountain. The third set crosses the landscape in a roughly N80E direction. The dikes in this third set are roughly parallel to one another and are the longest and oldest of the dikes. This third set of dikes was formed about the same time as the Sangre de Cristo Uplift, the event that pushed up the Sangre de Cristo Mountains between 2 north-south running fault lines about 27 million years ago. The Spanish Peaks, Silver Mountain, Mt. Mestas, the White Sisters, the Sheep Mountains, and the Black Hills in Huerfano County, along with their associated radial dike systems, were formed about 25 million years ago, east of the Alvarado Fault (which defines the east side of the Sangre de Cristo's) and east of the Dakota Wall. The volcanic plugs at Gardner, Huerfano Butte and Goemmer Butte were formed at the same time.

The dikes are granite. In the western portions of both Las Animas and Huerfano Counties there are some uplifted stone walls of the Dakota formation. They look like granite but are actually very compressed, very durable sandstone, part of a formation that runs from Canada to Mexico along the Front Range and eastwards. Other places where the Dakota Wall surfaces vertically are in the Flatirons area of Boulder, Garden of the Gods in Colorado Springs and the Garden of the Gods near Los Cerrillos, New Mexico.

As igneous intrusions, the granitic dikes also have deposits of quartz along them in many places. In those areas where the concentration of quartz is heaviest is where a prospector is most likely to find precious metals, like gold and silver. That's how Silver Mountain got its name. And back in the mid-1870's, there were between 50 and 60 gold and silver mines around the Spanish Peaks, mostly along the dike walls. Whatever ore there was played out quickly but there is still one gold mine claim open on the north side of the West Spanish Peak at the Bull's Eye Mine.