Another question which suggests itself in reference to the Leadville deposits is this: If the Leadville ore was once a mass of sulphides derived from the overlying porphyry by the percolation of surface waters, why has the deposit ceased?

The ore of the Walker and Webster and the Piñon is chiefly lead-carbonate and galena, often stained with copper-carbonate.

But if the process was similar to that in the Galena lead region, and the ores were originally sulphides, their formation should have continued and been detected in the Leadville mines.