History & Geology
Gold Depositiion and Gradients of Placer Streams—Part II
July 2012 by Jim Halloran
The steeper the gradient is, the more potential erosive power to move gold and other bedload sediments, and the more power to remove obstacles to flow.
The Golden Days of Julian, California
Some scattered reports say that gold may have been washed from streams here as early as the 1840s, but the undisputed major discovery came in 1870.
The Seven Troughs Mining District
The favorable geology of the northeastern and central parts of the Seven Troughs Range are the parts most interesting to prospectors. They are underlain by a thick sequence of Tertiary volcanic rocks, mostly rhyolites and andesites.
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.
Natural Gold Alloys
Natural gold is never 100% pure; all natural nuggets contain at least some impurities. We're going to take a look at just what some of those impurities might be.
The Wild Rush to Find More Cobalt—Part I
While some future cobalt will come from recycling lithium batteries and other products, the coming huge need for cobalt is virtually a perfect storm of heavy demand and insufficient supply.
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.
Why Haven't They Mined This Claim?
Improvements in mining equipment and techniques, along with a higher gold price, make many mining properties profitable today that may not have been in the past.
Subscription Required:
The Bawl Mill
• The Life of an Independent Prospector
• Gold in Guyana—Part I: Porknocking on the Puruni River Road
• That Something Extra
• Prospecting for Copper Ores—Part II
• Metallic Trash—Scourge of the Prospector
• Gold Mining Boom in the Carolinas
• California Suction Dredging Update
• Mine, Baby, Mine!
• Hecla to Reopen Lucky Friday Mine
• Nova Scotia Shows It's Serious About Jobs & Mining
• Melman on Gold & Silver
• Mining Stock Quotes and Mineral & Metal Prices
