History & Geology
Benches and Fossil Placers
March 2013 by Jim Halloran
Unfortunately for us mortal humans, we have a poor perspective on geologic time. When we look at a landscape such as a stream valley, we see it only in two, or at the most, three dimensions. We have poor comprehension of the valley’s fourth and most important dimension—time.Sierra County Gold—Part I
...this county contained some of the richest placer ground found in all of California and still produces some pretty impressive finds to this day.
Confluence Placers
Confluences of placer streams are well known as concentration sites for heavy minerals. The basic reason is that...
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.
Iron Ores and Iron Mining
For more than 40 years, iron ore prices have been decided by private negotiations conducted between the largest of the iron miners and the largest steel producers. These two sides dominate both the spot and contract iron ore markets.
California: The Land of Big Nuggets—Part II
There are a number of Tertiary river channels in the area, most of which trend south-southwest. They tend to be steep, narrow, and rich with coarse gold.
All About Garnets
I get a lot of questions from prospectors about garnets, their value and what they tell us about the geology of some types of mineral deposits. So I thought it would be a good idea to take a closer look at the lowly garnet and learn a bit more about it.
Understanding Large Gold Deposit Types: Discovering New Mines
The other opportunity that I see is in seeking unusual types of deposits. Specifically, the prospector would be searching for the stuff no one (or almost no one) is searching for. These deposits are effectively hiding in plain view.
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