History & Geology
Gold Deposition and Gradients of Placer Streams—Part I
June 2012 by Jim Halloran
When placer miners from the gold rush era began experimenting with the slope of their sluices, they must have pondered the ideal slope for trapping gold in a creek bed too. Logic suggests the same is true for streams...
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The Verde Copper-Gold-Silver-Zinc District, Jerome, Arizona
When I was a student in the College of Mines at the University of Utah, the Verde district was used as an exploration model for “submarine volcanogenic massive sulfide deposits.” So I looked forward to visiting this district and the town of Jerome in central Arizona in the spring of 2012.
Critical Minerals: Titanium—Part II
There are both hard rock and beach sand types of titanium deposits, but the hard rock deposits need to be at least 10 percent titanium while the beach sands often are economic with only two or three percent titanium.
Understanding and Prospecting Benches
The most obvious benches are usually near the valley floor, but they can be thousands of feet above the valley floor. Since benches were made by streams, they can contain placer deposits.
The Goldfield Mining District, Nevada—Part II
The majority of the gold produced in Goldfield has come from ores that are close enough to the surface to be oxidized by the air. This oxidized ore is normally a soft, shattered, earthy material usually stained yellow to brown by oxides of iron.
Las Médulas—The Gem of the Roman Gold Mines
This mine was a real wonder of engineering, and the water supply and drifts had to be carefully managed to keep it in operation. In fact, it didn’t close due to lack of gold, but instead closed with the fall of the Roman Empire.
Placer Gold Deposits of New Mexico
While a large number of locations have yielded some placer gold, most of the state’s placer production has come from a few productive districts.
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