The Tombstone Silver-Lead District, Arizona
April 2016 by W. Dan HauselIn 1877, a prospector named Ed Schieffelin discovered silver in “the middle of nowhere” and staked two claims: “Tumbstone” and “Graveyard.” Soon a town and mining district were organized and acquired the name “Tombstone” after making a spelling correction.
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.
Even though these were some of the earliest placer deposits to be worked, there is still plenty of gold left today—it just takes more work to recover. Knowing about the old locations where gold has been found is the first step to success.
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 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.
The specific gravity of chalcedony is 2.58 to 2.64. This is slightly lower than coarsely crystalline quartz because of slight porosity in chalcedony. Being so light, it will easily wash out of a gold pan.
A few quick calculations show that approximately 11 tons of gold are lost each year just in the manufacture of new cell phones.
The Robinson is a wooden bucket-line dredge that was built in the early 1900s in New York and shipped in pieces to Nash County in North Carolina by train for reassembly.
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