In 1871, two prospectors brought a sack of diamonds to the Bank of California, but refused to say where they found them.  The prospectors, John Slack and Philip Arnold, were cousins from Kentucky.  They allowed some San Francisco capitalists to buy the deposit from them - but the capitalists insisted on inspecting the mysterious diamond deposit in person.


San Francisco mine promoter and fellow Kentuckian Asbury Harpending was the main contact between the prospectors and the other investors. Harpending’s role in the affair has always been controversial.

The diamond investors needed to change the federal mining law to allow them to claim the diamond deposit. To accomplish this, they gave shares to Congressman Benjamin Butler. Butler saw to it that the law was changed to their satisfaction.


Slack and Arnold bought uncut diamonds in London, and planted them on this flat butte in northwest Colorado.  The mountain in the background is still called Diamond Peak.

Englishman Alfred Rubery had been arrested with Harpending during the Civil War, when the two joined in a plot to arm a warship in San Francisco to prey on Union shipping on the Pacific coast. In 1872, Rubery’s marital problems back in England prompted him to accept Harpending’s invitation to join in an expedition to the mystery diamond deposit.  


The diamond investors kept the Colorado location a secret. By accident or design, popular rumor placed the diamond deposit somewhere in Arizona or New Mexico.

Arnold and Slack had worked for Harpending at the mines near Ralston City, New Mexico, misleading some into thinking that the diamonds were found nearby.

The town, since renamed Shakespeare, is open to tourists.


Geologist Clarence King was studying western mineral deposits for the federal government. He and his team of geologists tracked down the mystery diamond fields, and after a few days of study, decided that the diamonds had been planted.

King’s exposure quickly stopped the swindle, but not before Philip Arnold hurried back to Kentucky with a sizeable pile of cash.

The incident gave Clarence King an international reputation as a geologist of unquestioned astuteness and honesty. He later became head of the U.S. Geological Survey.

Phil Arnold hurried back to his native Kentucky. He used his loot to bought a bank, and died a few years later. John Slack, who had sold out early in the scheme to his cousin Phil Arnold, moved to White Oaks, New Mexico, where he lived quietly and worked as an undertaker until his death in 1896.


Suspicion of his role in the Great Diamond Hoax dogged Asbury Harpending for the rest of his life.  Years later, he wrote his autobiography to refute the suspicion. 

Territorial governor of Idaho Caleb Lyon started another false diamond rush, this one in southwest Idaho.

Lyon - Libr Congr02

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