Re: Conjecture

No conjecture required.

In the early days, ores were smelted locally. However, the ores of the San Juans are complex and difficult to smelt - and the region doesn't have good sources of other materials required in the smelting process, namely fluxing agents.

In the 1880s and 1890s, most of the local smelters went away but the ores were still reduced and concentrated locally. And it was those concentrates that were sent out to smelters in Durango, Leadville, and even as far away as New York. While some very high-grade ores could be sent out for direct smelting, the large majority of material sent out was concentrates.

At the time, it was not wholly uncommon for smelters to be their own entities, and as such offered custom smelting runs on a contractual or case-by-case basis.

In short, the answer to your question is "many places" but not uncommonly Durango and Leadville.