ARKANSAS A-Z: State park site holds unique diamond-bearing formation

Postcard advertising diamond mining at Murfreesboro (Pike County); 1967
(Courtesy of the Butler Center for Arkansas Studies, Central Arkansas Library System)
Postcard advertising diamond mining at Murfreesboro (Pike County); 1967 (Courtesy of the Butler Center for Arkansas Studies, Central Arkansas Library System)

Almost 100 million years ago, in what is now Pike County, nature created one of the world's most unusual diamond-bearing formations, the big volcanic "pipe" that now serves as the centerpiece of Crater of Diamonds State Park. Famous today for recreational mining, the eroded old crater once inspired generations of diamond hunters to dream of commercial success.

Although the formation was recorded decades earlier, the search for diamonds began in 1888 when State Geologist John C. Branner and chemist Richard N. Brackett conducted a thorough survey and classified the rock as "peridotite"-- an olivine material similar to the "blue ground" of the rich diamond-bearing pipes found recently in South Africa (later known as "kimberlite").

The first person outside of South Africa to discover diamonds at their original source was John Wesley Huddleston, who saw the first crystals accidentally in summer 1906, on the surface of his farm near Murfreesboro. That 243-acre tract, bought in July 1905, included over three-fourths of the volcanic formation.

Beginning in September, an alert group of Little Rock businessmen, led by Sam Reyburn, obtained options on Huddleston's land and most adjacent properties. Following Huddleston's lead, the new venture began at the base of a big slope on the southeast side of the formation and soon found an extraordinary number of diamonds at the surface. Erosion had concentrated these within a layer of rocky, humus-enriched "black gumbo" averaging about a foot thick and extending at places to 4 feet. They usually turned up after vegetation was cleared but also could be screened from the topsoil with even the most primitive equipment.

The highest recorded average yield ran slightly over 36 carats per 100 loads (the standard 1,600-pound tram load). Although exceptional, the yield would have run considerably higher if the equipment of that time had retained very small diamonds instead of letting them pass back onto the field.

Field workers finally dealt with the black gumbo by adopting a technique applied in Western gold fields -- using high-pressure water hoses to break down the soil and flush material through sluice boxes, where heavy minerals were collected for regular processing. Between 1914 and December 1932, sluicing crews stripped the surface layer from over 50% of the big southeast slope.

Of perhaps 20,000 diamonds recovered, three were unusually large for the Pike County formation: a canary-yellow beauty weighing 17.86 carats (1917); a fair 20.25-carat white specimen (1921), and the record-setting Uncle Sam Diamond, a brilliant 40.23 carats (1924). The overall yield averaged about 10% gem quality, with the remainder an exceptionally hard industrial grade. Experts declared the gems at least as brilliant and valuable as those produced in South Africa or South America.

Compounding the excitement, prospectors soon found other peridotite deposits near the first discovery, and the fever of speculation led to the rise of new ventures such as American Diamond Mining Co., the Kimberlite Diamond Mining and Washing Co., and the Ozark Diamond Mining Co. This speculative heyday faded in 1909, producing very little except crushed expectations and growing skepticism.

The big formation itself raised doubts whenever Sam Reyburn's group, finally organized as the Arkansas Diamond Co. (ADC), concentrated on the crucial matrix. The highest recorded yield from peridotite on the southeast slope came from 482 loads washed in 1909: an average of 2 carats per 100 loads, or only about one-sixth of the average needed for minimal commercial production.

After 1922, the ADC worked the surface for almost three years before halting all activity. Finally, in July 1930, the struggling ADC was dissolved. The ADC's experience was repeated on a much smaller scale among other outfits. After the Depression, however, various mining interests pressed for renewed testing of the dormant Pike County field. The U.S. Bureau of Mines responded in 1943-1944 with its own evaluation of the southeast slope: slightly less than 2 carats per 100 tons avoirdupois.

After Crater of Diamonds State Park opened in 1972, commercial pressure started growing again, with some optimists speculating the big pipe in Pike County could hold as much as $5 billion worth of diamonds. A joint state-private venture finally evaluated the entire pipe and, in 1997, reported an overall average of 0.57 carat per 100 metric tons. Concluding the affair, the State Parks, Recreation and Travel Commission voted to impose a 20-year ban on further applications for commercial testing; the Legislature followed with a permanent ban.

Today, the ancient volcanic pipe fills a compatible role as regular "diggers" and other recreational miners work the plowed 35-acre field. Notably, a large number of diamonds found at the state park have come from a network of buried drainage channels holding material left from the processing of the surface layer in the early commercial era. -- Dean Banks

This story is adapted by Guy Lancaster from the online Encyclopedia of Arkansas, a project of the Central Arkansas Library System. Visit the site at

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