History & Geology
Enrichment of Mineral Deposits by Weathering—Part II
April 2016 by Chris Ralph
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.
Placer Gold Deposits of Utah
The placer deposits of Utah occur in two distinct types of environments. These are 1) placers found adjacent to, and derived from, gold, silver and base-metal deposits; and 2) placers found in major rivers and derived from unknown, distant sources.
Calcite and Limestone
The other distinguishing feature of calcite has to do with its chemistry. Geologists sometimes take a small bottle of dilute hydrochloric acid out into the field with them because calcite reacts with acids to make a bubbly foam.
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.
Placer Mining At Chititu Creek, Alaska
There is reason to believe these stream valleys are still rich with gold, silver and copper.
California's Mother Lode Quartz Veins
The actions of the hot, ore-bearing solutions are not limited only to the deposition of material within the walls of the fissures.
Exploring and Mining for Uranium
For a time uranium was more popular with prospectors than gold, but this is no longer true, and it has been decades since it was common to see individuals armed with Geiger counters out in the field.
Ophir—Possibly the Best Kept Secret in Alaska!
...I decided to excavate the semi-frozen high-bank that was resting on a soft shale bedrock footing. Within three feet, I encountered an intrusive!
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