Hamilton, Nevada

White Pine County, Nevada, USA. Hamilton's heyday was ephemeral even by the standards of mining rushes in the western US. Silver was struck in the late 1860s, at Treasure Hill off to the left of the pic, and a reported 25,000 hopeful miners swarmed the area in 1869. The bonanza ores were pretty much exhausted after a couple of seasons, however. Ore grades dropped off precipitously with depth (as discussed below), and altho a number of other, smaller orebodies were also worked in the area, nothing compared to the glory days. Some activity continues even now--an abandoned late 20th century building (leftmost inset) has joined the 19th century ruins and abandoned equipment (insets to right), but even the recent run-up in precious metal prices hasn't led to new mining. Hamilton itself lies at about 8000 ft/2440 m; note the snow patches persisting into mid-June. During active mining production shut down in the winter months! The high point on the skyline is Mt. Hamilton (10,745 ft/3275 m).

The original bonanza orebodies consisted largely of horn silver (cerargyrite, silver chloride, AgCl), and the occurrence (based on contemporary reports--nothing is left today!) was called perhaps the most extraordinary in the world. Cerargyrite is a product of near-surface alteration, so-called "supergene enrichment," and this is why the ore grades didn't persist at depth. The original silver sulfides oxidize, yielding sulfuric acid, which leaches away while the released silver precipitates with chloride from groundwater. The mechanism wasn't understood at the time; hence all the money sunk into sinking more shafts, looking for the (nonexistent) continuations of the bonanza veins! To be sure, Hamilton wasn't the only place this mistake was made--