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Placer Gemstones
December 2001 by Edgar B. Heylmun, PhD
Only the so-called “precious gems” will be considered in this article. They are diamond, ruby, sapphire, and emerald. A “gem” must be rare, hard, and durable, and possess a unique color or quality in order to be classified as a gem.Additional articles that might interest you...
Gold in Northern Baja California
November 2000
The 760-mile-Iong Baja California peninsula, in Mexico, separates the Gulf of California (Sea of Cortez) from the Pacific Ocean. Most of the peninsula is a desert where the traveler can find some of the weirdest plants on Earth...
The 760-mile-Iong Baja California peninsula, in Mexico, separates the Gulf of California (Sea of Cortez) from the Pacific Ocean. Most of the peninsula is a desert where the traveler can find some of the weirdest plants on Earth...
Ask the Experts
August 2014
Centrifugal bowls versus jigs
Centrifugal bowls versus jigs
The American Hill Mine
September 2007
In the high country of the Tahoe National Forest is 160 acres of a patented mining claim dating back to its origin around 1853. This is well above the historic mining town of Michigan Bluff and past Deadwood—an old mining town...
In the high country of the Tahoe National Forest is 160 acres of a patented mining claim dating back to its origin around 1853. This is well above the historic mining town of Michigan Bluff and past Deadwood—an old mining town...
New Silver and Zinc Mine Slated for Montana
September 2012
Arizona-based International Silver Inc. is proposing an underground silver and zinc mine in Montana and has asked Butte-Silver Bow County to lease them the surface and mineral rights to hundreds of acres.
Arizona-based International Silver Inc. is proposing an underground silver and zinc mine in Montana and has asked Butte-Silver Bow County to lease them the surface and mineral rights to hundreds of acres.
The Fire Assay of Fly Eyes
July 2002
Colorado-Utah-Wyoming oil shale was first reliably discovered to contain gold and silver by the U.S. Bureau of Mines in the 1920s. Although most of this vast shale resource, up to 1,000 feet in thickness, contained nil or barely detectable values, many brown shale samples fire assayed here over the past thirty years have yielded up to 0.02 ounces per ton (opt) Au and 2.0 opt Ag.
Colorado-Utah-Wyoming oil shale was first reliably discovered to contain gold and silver by the U.S. Bureau of Mines in the 1920s. Although most of this vast shale resource, up to 1,000 feet in thickness, contained nil or barely detectable values, many brown shale samples fire assayed here over the past thirty years have yielded up to 0.02 ounces per ton (opt) Au and 2.0 opt Ag.
The Oregon Claim
December 2010
When I started dredging a short distance downstream from that feature I realized that I was into a major paystreak and much of the gold was coming right out of the upper gravel. I could see the chunky pieces falling out of the gravel as they were pulled into...
When I started dredging a short distance downstream from that feature I realized that I was into a major paystreak and much of the gold was coming right out of the upper gravel. I could see the chunky pieces falling out of the gravel as they were pulled into...
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