Crater of Diamonds State Park

Crater of Diamonds State Park is a 911-acre (369 ha) Arkansas state park in Pike County, Arkansas, in the United States. The park features a 37.5-acre (15.2-hectare) plowed field, one of the few diamond-bearing sites accessible to the public. Diamonds have been discovered in the field continuously since 1906, including the graded-perfect Strawn-Wagner Diamond, found in 1990, and the Uncle Sam, found in 1924, which at over 40 carats is the largest diamond ever found in the United States.
The site became a state park in 1972 after the Arkansas Department of Parks and Tourism purchased the site from private owners in Dallas, Texas, who had previously operated the site as a tourist attraction.
In August 1906, John Huddleston found two strange crystals on the surface of his 243-acre farm near Murfreesboro, Arkansas. The following month, Huddleston and his wife, Sarah, sold an option on the property to a group of Little Rock investors headed by banker-attorney Samuel F. (Sam) Reyburn, who undertook a careful test of the property. From the sub-surface diamond matrix, Reyburn's team extracted about two carats per hundred short tons of material (the standard tram-cart loads, each carrying about 1,600 pounds of material). Federal testing in 1943-1944 and State sponsored testing in the 1990s produced virtually the same result.
After 1906, several attempts at commercial diamond mining failed. The only significant yields came from the original surface layer on the east half of the Crater -- a black and sticky gumbo clay ranging from about one to four feet thick. Natural erosion, rocks, and vegetation had concentrated diamonds there over a long period of time.
In the early era, 1907–1932, companies finally gave up on conventional processing and adopted hydraulic mining to break down the black gumbo. That method was employed on a grand scale in California, to extract gold, and was already being used by one of Reyburn's competitors on six acres at the north end of the Arkansas diamond field. Available photos of Reyburn's property show large hoses spurting pressurized water, which carried material through sluice boxes where diamonds and other heavy minerals were concentrated for screening. Field crews also screened the pools of silt at the end of sluice boxes.
In Sam Reyburn's hydraulic testing, the "black gumbo" surface material often yielded about thirty carats per hundred loads, a very high number compared with diamond fields generally. No doubt many diamonds were lost in that process, including some large ones. In 1908 and 1943-1944, careful testing of the underlying volcanic breccia found about two carats per 100 tons. Pit testing sponsored by the State of Arkansas in the 1990s found virtually the same yield.
Because equipment of the early period usually included bottom screens with mesh larger than 1/16th inch, thousands of smaller diamonds were allowed to pass through during testing. The bulk of these ended up in shallow drainage cuts all over the diamond field and in the big natural drains on its east and west edges. Since the State of Arkansas acquired the Crater, in 1972, regular plowing on the east side has marked the main field, 30 to 35 acres of easily eroded breccia. In recent decades, the old east and west drains have been especially fruitful for recreational diamond diggers. The regular diggers have worked especially hard for recoveries from the east drain, about ten feet deep: runoff from the field buried much of that channel during the early era; bulldozers finished the job while preparing access for a later test. Notable diamonds from the bottom of the east drain include the flawless white Strawn-Wagner diamond, weighing 3.03 carats in the rough. Shirley Strawn of Murfreesboro, Arkansas, came up with this celebrated gem in 1990.
Huddleston's finds in 1906 hardly created a "boomtown" atmosphere around Murfreesboro. According to old tales, hotels in Murfreesboro turned away 10,000 people in the space of a year. Supposedly, aspiring diamond miners formed a "tent city' near the diamond field and named it "Kimberly" in honor of the famous Kimberley diamond district in South Africa. On the other hand, all available evidence indicates that the Town of Kimberly originated as a land-development venture in 1909, initiated by Mallard M. Mauney and his oldest son, Walter, on their land immediately south of Murfreesboro. The project failed soon afterward as speculative publicity generated by the diamond discovery collapsed. There is no evidence of a tent city. Today, the Kimberly area is almost all cow pasture owned by Mauney's descendants. As for any general diamond fever, that never developed: previous diamond-mining swindles in the American West had generated widespread skepticism. Before the State-sponsored testing of the 1990s, many observers still believed the Crater of Diamonds was "salted."
During WWII the U.S. government took control of the diamond field and enlisted the Glen Martin corporation to extract diamonds for industrial use. Although diamonds were obtained, the yield remained about the same as earlier tests, and even the federal government thought that would be too costly for mining.
After the war, the property reverted to the private owners. From 1951 to 1972, the crater hosted several private tourist attractions. The first, The Diamond Preserve of the United States, lasted about one year. In late 1951, Howard A. Millar stepped in and salvaged the infant tourist industry. In April 1952, Millar and his wife, Modean, launched their tourist attraction on a small north section of the diamond-producing field. Howard Millar, an accomplished writer and promoter, stirred unprecedented national publicity and drew enough visitors to sustain the operation. In March 1956, a visitor found the "Star of Arkansas" on the cleared surface. That rare beauty, clean and brilliant in the raw, weighed 15.33|carats, enough to generate unprecedented national publicity.
Later, Roscoe Johnston opened a rival tourist attraction, the "Arkansas Diamond Mine", on the main part of the diamond field. The rivalry between the two operations left both in a weakened position. In 1970, the entire volcanic formation was consolidated by a private partnership, which then reassigned the property to General Earth Minerals (GEM) of Dallas, Texas. GEM expected to turn the property over for a profit, but ended up heavily indebted to GF Industries (GFI) of Dallas. Upon default, GFI took the property in July 1971.
GEM consolidated the tourist operations as well as the property. GFI continued the attraction until it sold the 80-acre volcanic formation and a surrounding 800 acres to the State of Arkansas, in March 1972. The price: $750,000. The tourist operation continued as the centerpiece of Crater of Diamonds State Park.
Understandably, this special gem became closely associated with the State of Arkansas, "The Natural State." A large diamond symbol has dominated the state flag since 1912. The federal government issued an Arkansas State quarter coin in 2003. It bore a diamond symbol on its face, as did new Arkansas auto license plates.
The Crater of Diamonds is part of a 100-million-year-old eroded volcanic formation (a volcanic pipe). The deeply sourced Kimberlite/Lamproite magma brought the diamonds to the surface. The diamonds had crystallized in the relatively stable cratonic root of the continent long before and were sampled by the magma as it rose to the surface.
The geology of the area and the diamond formation process itself were the subjects of the Ph.D. dissertation of Roland Everett Langford in 1973 of the University of Georgia. In it, he proposed a gas phase reaction from the reduction of carbon monoxide and carbon dioxide in the upper mantle. The dissertation was on display at the state park for many years.
More recent research by geologist Dennis Dunn (Ph.D. dissertation 2002) found that the diamondiferous epiclastic rocks range from olivine lamproite to phlogopite and olivine-rich tuffs. The chemistry of the mantle xenolith was used to derive maximum pressures of around 5 GPa and temperatures of 1000 °C for the upper mantle origin of the lamproitic magma.
The lamproite diamond source is unusual, as almost all diamonds are mined from kimberlite formations and from alluvial deposits of diamonds weathered from that "hardrock" source. The most prominent lamproite diamond source is the Argyle diamond mine in Australia. It is notable that the physical characteristics of Australian lamproite and the Arkansas deposit differ markedly. From the discovery in 1906 into the 1960s, the historical record shows that geologists consistently classified the Arkansas deposit as Kimberlite.
Crater of Diamonds State Park is known for the 37.5-acre (15.2 ha) plowed field on which visitors can hunt for diamonds and other semi-precious gems. On average, two diamonds are found per day by park visitors. A visitor center contains information about the geology of the park, a gift shop, and a cafe. Interested visitors can continue to the Diamond Discovery Center, which offers an interpretive look at prospecting for diamonds. The Diamond Springs aquatic playground, enclosed pavilion, trails, and picnic areas surround the diamond field. The park offers campers 47 Class AAA facilities near the Little Missouri River.
Crater of Diamonds State Park is situated over an eroded lamproite volcanic pipe. The park is open to the public and, for a small fee, rockhounds and visitors can dig for diamonds and other gemstones. Park visitors find more than 600 diamonds each year of all colors and grades. As of 2015, over 75,000 diamonds had been found in the crater. Visitors may keep any gemstone they find regardless of its value.
In addition to diamonds, visitors may find semi-precious gems such as amethyst, agate, and jasper or approximately 40 other minerals such as garnet, phlogopite, quartz, baryte, and calcite.