The triangular area bounded by the most productive mining districts of central Colorado- Leadville, Climax-Kokomo, and Gilman-Red Cliff- is of economic interest not only because of its close spatial relation to these districts but because it is closely related geologically. It contains the same rocks as the adjoining mining districts and is closely related to them structurally. It shows widespread evidence of weak mineralization at the surface and may contain ore deposits at depth, as the zones that have been productive in the adjoining mining districts lie beneath a cover of younger rocks in much of the area.