History & Geology
Mineralized Faults and Contacts in the Search for Gold
January 2016 by Chris Ralph
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.
The Ely Copper-Gold District of Nevada
The main ore deposits of the Ely district are associated with an east-west belt of altered and mineralized rocks measuring about one mile wide that extends 8 miles westward from Ely.
Critical Minerals: Tungsten
Because tungsten minerals are heavy, exploration can be done using stream sediment samples. Prospectors looking for gold have found scheelite or wolframite in their placer concentrates, and in some cases this has led them to make important tungsten finds.
Diary of a Diamond Prospector
I couldn’t wait to get started. With no field budget, an assay budget of $100/year, a 1975-Ford Bronco that was a road hazard, a gas card, a topo map and full support of the director, I headed to the State Line district near Tie Siding along US Highway 287 to begin mapping kimberlite.
Gold in Beatty, Nevada
In this case, signs of gold were found at the bottom of the alluvial and then traced in a triangle up the face of the mountain until they stopped—that is where the digging began.
The Strange History of the Utica Mine
In the summer of 1854, John Selkirk, a discouraged placer miner who was down on his luck and ready to go back to Massachusetts, tied his mule up in a gulch north of what is now downtown Angel's Camp.
Enrichment of Mineral Deposits by Weathering—Part II
While both zinc and lead deposits also are enriched by the surface weathering process, in part two we will look at the enrichment process for copper and also gold deposits, and at the interpretation of leached outcrops to figure how rich the concentrated deposits below them may be.
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