The Ortiz Mountains are part of the larger Ortiz porphyry belt of Santa Fe County, and consist of late Eocene to early Oligocene intrusive igneous rocks and their sedimentary host rock. Other members of the Ortiz porphyry belt are South Mountain, the San Pedro Mountains and the Cerrillos Hills. These porphyry intrusions were followed by movement on the Tijeras-Canoncito fault and later mid Oligocene (31.4-27.9 ma) intrusions of stocks and dikes with mineralization including both base and precious metals.