From Gail Heriot on Instapundit:
If you’ve ever been to NW Colorado, you may have seen Diamond Peak. If you’ve wondered if there are diamonds there, the answer, sadly, is no. But there is a story—one the San Francisco Chronicle called “the most gigantic and barefaced swindle of the age.”
It concerns two prospectors (or, more accurately, two grifters)—the flamboyant Philip Arnold, a Kentuckian born in the same county as Honest Abe Lincoln, and his taciturn cousin John Slack. Arnold had worked for a short while at the Diamond Drill Co. During that period, he had “acquired” a number of uncut industrial-grade diamonds. The diamonds were not especially valuable, but they looked impressive—enough so to thrill several San Francisco investors.
The cousins had a knack for causing such thrills. They told investors that they had found a huge diamond deposit. They appeared concerned—almost overly concerned—about keeping the location of their find secret. This only intrigued investors.
There’s a reason they called this the “Great” Diamond Hoax. Arnold and Slack could have taken the initial relatively modest amounts they were given as investments and run. But instead they traveled to London under assumed names, purchased more uncut diamonds and returned to San Francisco with more “proof” of their find. The list of willing investors grew and grew. It included Charles Tiffany, General George B. McClellan, and General (and Congressman) Benjamin Butler, among many other prominent citizens of the day.
These investors weren’t complete idiots. They insisted that a well-respected mining engineer be taken to the location and examine the evidence. But the engineer—Henry Janin—was duped by the diamonds and other precious stones that the cousins had “salted” the ground with.
The eventual hero of the story was Clarence King, a Yale-educated geologist, who was born on this day in 1842. He and his team of government surveyors had been carefully mapping out the large mountainous area around the so-called diamond field. They happened to be on the same train with Janin, who talked about what he had seen. King was alarmed at the story in part because he feared it would reflect badly on his work to have missed any evidence that such a find was possible.
Although winter was fast approaching, he took his team to the area Janin had described and eventually found the sign for the cousins’ claim. It didn’t take long for him to determine that it was an elaborate hoax. The diamonds and other precious stones were implausible places. The plausible places had no diamonds. The kinds of stones that were placed together would not be naturally found together.
He blew the whistle and the scheme came crashing down, much to the embarrassment of some of America’s most prominent citizens.
There’s more at Smithsonian Magazine.