Third-day road log, from Grants to Milan, Homestake Mining Company, Dos Lomas, Haystack Mountain and El Tintero
— Spencer G. Lucas, Andrew B. Heckert, William R. Berglof, Larry S. Crumpler, Jayne C. Aubele, Barry S. Kues, and Virginia T. McLemore

The field conference ends today, focusing on uranium mining, mill site and tailings reclamation and the late Cenozoic volcanic rocks to the northwest of Grants. Today’s trip begins at Stop 1 with a tour and explanation of the Homestake Mining Company reclamation project near Grants. Homestake was a major producer of uranium ore from the Ambrosia Lake District to the north of today’s route, milled the ore at this site, and has been reclaiming the mill tailings for more than two decades.

At Stop 2 near Dos Lomas (a topographic feature) we examine a well-exposed sandstone pipe in the Bluff Sandstone and discuss uranium deposits in the Todilto Formation, together with their mining history and the origin of the intraformational folds that localized the uranium mineralization in the Todilto.

We then move on to Stop 3, between El Tintero volcano and Haystack Mountain (also known as Haystack Butte). El Tintero, with an estimated age of 30-120 ka, was the source of an extensive series of lava flows (the “Bluewater flow”), some of which are crossed by I-40 west of Grants (see road log for Day 2). Uranium in the Todilto Formation was discovered for mining at Haystack Mountain, and one of the largest known Todilto deposits was mined there. Indeed, uranium mining in New Mexico began at Haystack Mountain.