Placer gold was discovered in 1859 in California Gulch, about seven
miles north of the present town of Leadville. The rush that followed was
short but sweet; the camp was called Oro—gold! About $5,000,000 was
produced from the placer mines within two years, though by 1861 the area
was all but deserted, for the easily won placer gold was gone.
[Illustration: Early-day Leadville sprawled among its mine dumps at an
elevation of 10,200 feet. The Sawatch Range, in the background,
contained many smaller mining communities, now deserted. Mt. Massive,
the state’s second highest peak, forms the crest of the continental
divide here. (State Historical Society of Colorado photo)]
In 1875 a smelter was erected a few miles downstream from Oro to process
cerussite—silver-rich lead carbonate—that occurred in the placer sands.
For years this mineral had been considered a nuisance because, being
much heavier than sand, it tended to separate out with the gold. The new
town of Leadville sprang up near the smelter and shortly afterward more
lode deposits were discovered south of the placer workings. From $63,000
in 1875, production climbed to $2,500,000 in 1878 and more than
$15,000,000 in the peak year of 1882.
Geologically, the ores of this district occur as Tertiary replacements
and veins in Ordovician, Devonian, and Mississippian limestones. The
“Blue” or Leadville Limestone, of Mississippian age, contains the
richest ore. Ore deposits were formed after the limestones had been
faulted and cracked extensively by mountain-building movements; the ores
themselves probably crystallized from molten or gaseous materials
involved in related igneous intrusions. River gravels and glacial debris
mask the true nature of the lode deposits, but studies in the mines show
that the fault systems along which ores are deposited trend north or
north-northeast.
The Leadville district is now experiencing its third mining boom as a
newly recognized lead-zinc orebody is being developed. Production is
expected to reach 700 tons of ore per day by 1971. Total production of
gold, silver, lead, zinc, and copper in the district has reached
$500,000,000.