As defined here, a gem is any jewel, whether stone or pearl, having value and beauty that are intrinsic. A gemstone or gem material is a stone or material from which a gem may be cut. Gems are used for personal adornment, display, or in manufactured objects of art because they possess beauty, rarity, and durability. Arkansas has within its borders several stones or materials which, by popular definition, are considered gemstones. They are: amber, diamond, onyx , pearls, (fresh water), quartz (several varieties), and turquoise. In 1995, Arkansas ranked 3rd in the nation in value of gemstones produced ($4.89 million).
Amber is brittle, yellowish to brownish, translucent to transparent, fossilized tree resin. It may enclose insects and other organisms. Gem-quality amber takes a high polish. Gem-grade amber is often used to make faceted beads and irregular shaped polished drops. Larger pieces may also be manufactured into mouth pieces for pipes or cigarette holders, although less expensive plastics now substitute almost entirely for this market. Amber has a low specific gravity (1.0-1.1) and is soft (2-2.5 on Mohs scale). Amber burns with a strong "tar" odor due to its hydrocarbon composition. Amber is also soluble in some petroleum-based solvents, such as acetone.
Worldwide, amber is recovered from alluvial soils, clays, recent sediments, beds of lignite, and along some seashores where offshore deposits are disturbed during storm activity, as the Baltic Sea. In Arkansas, amber is associated with lignite beds of Tertiary age uncovered during the mining of brick clay south and east of Malvern in Hot Spring County. Although no gem-grade amber has been reported in these deposits, paleontologists have discovered several new species of insects in Arkansas amber.
The 1967 Arkansas General Assembly passed legislation which became Act 128 designating diamond as the official gem of the State. A number of diamonds recovered from the volcanic pipes near Murfreesboro qualify as gem-grade material. The largest diamond discovered in the United States came from this site and was recovered by commercial methods. Named the "Uncle Sam", this diamond was discovered in 1924. It weighed 40.23 carats in the rough, and was faceted into an elongate emerald-cut gemstone weighing 12.42 carats. It has a faint rose color and is presently owned by Peiken of Fifth Avenue, New York.
17 carat Arkansas diamond crystal from Pike County from the Roebling collection in the US National Museum (Smithsonian). Photo by Chip Clark.
The best known diamond recovered by a tourist is the "Star of Arkansas", a white 15.33-carat crystal which was faceted to a flawless 8.27-carat marquise-shaped gem. This stone was auctioned at Christie's of New York in 1994 and brought $145,000. The largest diamond discovered since the beginning of Crater of Diamonds State Park in 1972 is the "Amarillo Starlight", weighing 16.37 carats. This stone was faceted to a 7.54-carat marquise-shaped gem, valued at between $150,000 and $175,000.
Records of diamonds discovered at Crater of Diamonds State Park for the period of 1972 to 2007, inclusive, indicate that 734 diamonds were reported that weighed over 1 carat each (Crater of Diamonds State Park, Diamonds Statistics Summary). Some of these stones would qualify as cuttable gemstones.
A particularly notable recently discovered diamond that was cut and found to be a flawless perfect top quality colorless stone is the Stawn-Wagner diamond. It weighed 3.03 carats rough and was cut to a brilliant round gem of 1.09 carats. Gemologists have graded the stone as grade D-flawless, 0/0/0 (cut, color, clarity) and stated that this diamond is one in a billion! It was purchased by the Crater of Diamonds State Park for $34,500 in 1999, using part grant money and part private donations. This flawless gem may be viewed at the Park.
Active mining operations ceased with the destruction of the first mills by fire in the early 1920s. No commercial operation has existed since that time although several major and a number of minor diamond exploration companies have investigated both the Prairie Creek and several adjacent smaller pipes, particularly in the 1980s and early 1990s. The Prairie Creek, being a state park, is now by law excluded from further commercial examination.
Onyx is a variety of banded calcite (CaCO3) deposited by water in caves. Inexpensive carved figurines, table tops, and interior decorative items are the stone's principal uses. There are numerous caves in northern Arkansas. Currently, it is illegal to remove or disturb cave formations in the state. Arkansas has no recorded history of use of this resource.
A pearl consists of concentric layers of the mineral aragonite (CaCO3) formed as nacre secreted by a mollusk to cover an internal irritant. Pearls are recovered from fresh- and salt-water bivalve shellfish. In Arkansas, fresh-water mussels of the genus Unios are the principal source of pearls. A pearl's value depends on its weight, luster, perfection of shape (sphericity), color, translucency, and stability in air. The luster and translucency are controlled primarily by the thickness of the nacre. It is difficult to grade the value of any given pearl without considerable experience.
Although pearls were occasionally collected by Arkansas's fishermen, little notice was taken until 1895, when a survey party recovered pearls from fresh-water mussels in the White River. When this collection of pearls sold for $5,000, many people began to search for the gems in the White, St. Francis, and Arkansas Rivers and their tributaries. Within a year, nearly every major stream in Arkansas had yielded pearls. The highest quality and most extensive collections came from the White and Black Rivers in north-central and northeast Arkansas. The pearling industry was centered at Black Rock, Independence County, where, at one time, more than 1,000 people were gathering pearls within 20 miles of the town. The Black River proved to be the nation's richest pearling region. During the early years of pearling excitement in Arkansas, a large percentage of the choice pearls were discovered loose, lying in mud along cutoff meander lakes and river backwater shorelines. At the height of the excitement in 1897, many people purchased unopened mussels, speculating on the discovery of valuable gems. Between l895 and 1898, over $500,000 worth of pearls were recovered by Arkansas's pearling industry.
Individual Arkansas pearls have sold for up to $25,000, but pearls valued up to a few hundred dollars are considered exceptional. The $25,000 pearl was round, weighed 103 grains (almost one-quarter ounce), and was discovered in the Black River in 1904. A necklace displayed at the St. Louis World's Fair in 1904 was composed of 16 Arkansas pearls which had a combined weight of 861 5/8ths grains (nearly 2 ounces). A pearl found at Newport, Arkansas, is set in one of the Royal Crowns of England. Usually fresh-water pearls do not compare with salt-water pearls, but the exceptional luster and color of some fresh-water pearls do command high prices.
Presently, Arkansas has one commercial pearl business, Pearls Unique of Newport, Jackson County. Arkansas continues to be second in commercial freshwater pearl recovery in the United States, Tennessee being first.
Gemstone varieties of quartz (SiO2) present in Arkansas include the cryptocrystalline varieties (agate, jasper, chalcedony, banded chert) and crystalline varieties (rock crystal, amethyst, smoky quartz). Another material potentially usable by lapidaries is silicified petrified wood. Opal, a non-crystalline form of silica is discussed in this section also.
Arkansas is often thought of as offering little material for the lapidary, other than quartz crystal and diamond. However, for the hobbyist interested in tumble polishing and cabochon making, much useful material is present.
Agate is translucent cryptocrystalline quartz which displays distinct banding. Most agate collected in Arkansas is present in gravel deposits on Crowley's Ridge, although agate can occur wherever gravel is present. Crowley's Ridge extends north-south from Clay County to Phillips County in a gentle eastward-facing arc. The agates in this area are different shades of tan, light brown, and yellow due to the penetration and oxidation of trace amounts of iron. The gravels of the Crowley's Ridge deposits were transported to their present position by the ancestral Mississippi River. Identically banded, light bluish-gray agate is present in Missouri in the Potosi Formation (Upper Cambrian). This rock unit may be the source of the bulk of the agate in the Crowley's Ridge deposits. Oxidation of the gravel-bearing units has altered the original blue-gray color to shades of brown and yellow. Rarely, a specimen may appear similar to the agate from the Great Lakes area of the northern United States. Agate is also moderately common at the Crater of Diamonds State Park, where it sometimes displays a lace-like pattern. The agate is present as blocky rectangular pieces weighing up to several pounds and is present in the major drainages of the diamond-search area. They are somewhat sugary or porous in texture, rendering it unusable to the lapidary. However, good-quality pieces are not uncommon and yield attractive cabochons in a variety of colors, some being suitable for tumble polishing.
Amethyst as a gem material is a violet to purple, transparent, crystalline variety of quartz. The Crater of Diamonds State Park, 2.5 miles southeast of Murfreesboro in Pike County, is the only area in Arkansas known to contain crystals of amethyst large enough to be of use to the lapidary. Amethyst veins, some a foot wide, are sometimes located by collectors during the periodic plowing of the diamond search area. The amethyst is present as stubby strongly colored crystals up to 1 inch across, filling cavities in calcite veins. Individual specimens are scarce and the amethyst crystals may be zoned or contain tiny inclusions of goethite (an iron mineral), strongly resembling the amethyst of Brazilian geodes. Although some percentage of this amethyst may be faceting quality, most is suitable for producing tumbled stones.
Chalcedony is a light-colored, translucent, nonbanded variety of cryptocrystalline quartz which has a waxy luster on a broken surface. It is often nodular and sometimes is fluorescent green in ultraviolet light. Cream-colored masses of chalcedony reportedly have been recovered from the gravel deposits of the Saline River in Saline County.
Chert is an opaque to translucent cryptocrystalline variety of quartz, which ranges considerably in color and suitability for lapidary use. Although the Ouachita Mountains contain major beds of sedimentary chert, very little is of cuttable quality. Major sedimentary units in northern Arkansas do contain banded translucent nodules of chert that will take a high polish when tumbled or cut into cabochons. Nodular chert in the Cotter Formation (Early Ordovician) and in the residuum formed by its weathering is often available in attractively banded pieces. Large unfractured examples are somewhat scarce, but abundant tumbling-quality material is available, particularly in Marion County, and also in portions of Carroll, northern Boone, Baxter, Fulton, Randolph, Sharp, and Izard Counties. This is the major outcrop area of the Cotter Formation. Some chert which will take a high polish is also present in the Penters Formation (Devonian) and, locally, in the Boone Formation (Mississippian) and its residuum in north Arkansas. All of these materials are present in shades of brown, tan, cream, and gray. Large quantities of tan to brown chert are also present in the gravel deposits along Crowley's Ridge.
Jasper is a red variety of chert. Two companies, one in Pike County and the other in Hempstead County, have reported the recovery of small quantities (less than 1,000 pounds yearly) of jasper for several years. The suitability of this material for lapidary use is unknown. The source of the jasper may be the basal gravel deposits of the Cretaceous formations or Quaternary deposits which contain reworked gravels derived from the Cretaceous units. The jasper probably originated as red novaculite. Jasper is also present at the Crater of Diamonds State Park, Pike County, as rounded reddish-brown to red surficial gravels in the diamond search area. The jasper takes a high polish and may be used for tumbling and cabochon making. Small amounts of jasper is present in the gravel deposits of Crowley's Ridge in northeast Arkansas.
Although opal is not quartz mineralogically, it is discussed here because it is an amorphous variety of silica (SiO2) and can occur anywhere ground water has circulated. Opal usually contains an indeterminate quantity of water so the chemical formula is written as SiO2. nH2O. A colorless transparent variety called hyaline is relatively common in Arkansas as late-formed glassy blebs or crusts coating other minerals. Hyaline is commonly fluorescent green due to traces of uranium salts. No site in Arkansas has yielded significant material for lapidary use.
At the Potash Sulphur Springs intrusion in Garland County, late secondary opal was discovered in the zone of contact metamorphism as both greenish-yellow veins having black dendritic (fern-like) patterns and as gray, opalized replacements of the contact rocks. In the North Wilson pit at this site, paper-thin films of fiery precious opal were noted in a very restricted zone in the vanadium orebody.
In southern and eastern Arkansas, wherever petrified wood is present, there is the possibility of discovering late-formed hyaline opal. See the section on Petrified Wood.
Silicified petrified wood is present in Quaternary gravel deposits in eastern and southern Arkansas. Because most specimens are cream to white in color, little interest has been expressed by hobbyists in cutting and polishing the material. A fossilized "logjam" of this type of petrified wood was reported in a stream drainage at the golf course of the El Dorado Country Club in Union County. Many people in southern Arkansas use light-colored petrified wood as flower-garden decoration pieces or borders. Late-formed hyaline is often present as colorless botryoidal infillings of cavities or fractures in the petrified wood. Some petrified wood in the gravel deposits along Crowley's Ridge ranges in color from tan and brown to black and takes a high polish. This material is suitable for cabochon making and tumble polishing. Numerous small pieces and sometimes large logs of petrified wood are collected in the creeks that drain Crowley's Ridge from Forrest City in St. Francis County northward to Wynne in Cross County
Rock crystal (quartz crystal) that qualifies as a gem material is transparent, colorless and should contain no visible flaws. This material is relatively abundant at several quartz crystal dealers in Arkansas and the price varies with size of the rough stock. When used for faceting stones or beads, carving figures or decorative items, or manufacturing spheres, it is not necessary that the crystal's exterior be undamaged as with prime specimen material. Because of the low price of surface-damaged rock crystal, it is a popular material to use when learning faceting techniques. Faceted rock crystal is sold at many tourist-based businesses in Arkansas under the trade name, "Hot Springs diamond". Slender, clear, undamaged single quartz crystals are known locally as jewelry points and are used in the manufacture of relatively inexpensive necklace drops, pendants, and earrings, often set in sterling silver settings. Rock crystal for this use ranges from $30 to more than $150 per pound, depending on its perfection, transparency, luster, and length of the crystals.
Smoky quartz as a gem material is light- to medium-brown in color, transparent, and of best quality when it is unzoned (uniform color). In Arkansas, most smoky quartz is present in two areas: near Jessieville in Garland County and adjacent to the Magnet Cove intrusion in Hot Spring County. Southwest of Jessieville, one mining operation occasionally recovers some pale- to medium-brown smoky quartz. These crystals range up to 3 inches in length and 1.5 inches across and have milky bases or areas near their attachment points to the vein walls. Most crystals exhibit faint zoning (alternating light and dark banding), but some crystals qualify as faceting material. Zoned and unzoned smoky quartz crystals to 6 inches long were mined in the late 1960’s at a site on the north shore of Lake Ouachita, west of Jessieville in Garland County. The area has since been closed to collecting by the U. S. Army Corps of Engineers. The deposits of smoky quartz at Magnet Cove have been known for over a century. The host rock, the Arkansas Novaculite (Mississippian-Devonian), is the source of the silica that was necessary to form the crystals. In this area, smoky quartz crystals have been discovered up to 15 inches in length and 6 inches across. Most of the smoky quartz from this area contains either internal fractures, zoning, mineral inclusions, or has sufficient internal stress that renders it useless for faceting stock. Small pieces are sometimes cut into attractive gems. Some of this material might be useful for tumbled stones. A site which yielded a small amount of faceting-grade smoky quartz was discovered by Ben Clardy, Arkansas Geological Commission, and investigated by state geologists in the 1970’s. It was a highly weathered quartz syenite dike in a bauxite mine in Saline County. Although about 50 pounds of rough smoky quartz pieces were collected, less than a pound was of faceting quality.
Most mineral dealers and rock shops in Arkansas have samples of "smoky quartz" on display. Much of this material is natural rock crystal that has been subjected to gamma radiation in a reactor, causing the crystal to turn almost black. Quartz dealers have been marketing this irradiated quartz for many years, largely for decorative purposes.
The mineral turquoise (Cu2+Al6(PO4)4(OH)8 . 4H2O) is the end member of a mineral series in which copper is substituted for iron; chalcosiderite is the other end member. Intermediate in composition in the series between these two minerals are the minerals planerite and rashleighite. However, to the lapidary, any and all of these minerals are considered turquoise if the material will cut and polish. Hand-crafted turquoise and silver jewelry has become increasingly popular with the general public.
In Arkansas, turquoise group minerals are present in the Ouachita Mountains, usually associated with the secondary mineralization present in lead-, zinc-, and copper-bearing quartz vein deposits as thin fracture-filling seams in the sandstone or shale host rock. In some places turquoise is present as hard, translucent bluish films where no primary copper mineralization is evident. In these instances, the host rock is almost always the Arkansas Novaculite (Devonian-Mississippian) or the Bigfork Chert (Ordovician). Planerite is often associated with either secondary aluminum phosphates or manganese mineralization.
Three localities of "turquoise" mineralization are notable in Arkansas. In 1974, a turquoise prospect on Porter Mountain in Polk County was tested by a company based in Denver, Colorado. The company reported that about 200 pounds of fair to good gem-quality turquoise had been processed from this location, of which about 10 pounds were sold for $100 per pound. The host rock is tripolitic novaculite. The site, named the Mona Lisa mine, was intermittently mined by open-pit methods, with a reported total recovery of over 1,000 pounds, until the late 1980’s. Much of the output of the Mona Lisa mine was dyed, stabilized, and compressed into cylinders for shipment to China as carving stock. Some treated and untreated gem material was marketed in New Mexico and Arizona. Final reclamation took place on this site between 1989 and 1991. Another locality in Polk County is the Coon Creek manganese mine. Planerite is moderately abundant as thin green films coating novaculite boulders and cobbles. However, no gem- or cutting-grade material is located at this site. Planerite was also abundant at the Montgomery County quarry on Mauldin Mountain, Montgomery County. Planerite formed as thin coatings and crusts on Bigfork Chert, often in association with wavellite, an aluminum phosphate. No gem material is located at this site.
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