Chalcedony, the beautifully colored cryptocrystalline quartz that could be precisely carved into seals and amulets, was a treasured gem of the ancient world. No important Roman would be without a seal or signet ring carved in this fine and durable material. The Victorians, too, prized chalcedony for carved cameos and intaglios: its fine texture allows for delicate and intricate workmanship.
Jewelry designers today love its glowing translucent tones and its availability in a wide range of colors and shapes. Chalcedony truly is a darling of today's gem carvers and jewelry designers. Piece after piece is featured in magazines like Lapidary Journal, Modern Jeweler, Metalsmith and Ornament. One look at the ethereal colors in this group will tell you why.
The prices and value of chalcedony can vary tremendously, depending on the size and quality of the gemstone.
Why Buy Loose Gemstones Instead of Pre-Set Jewelry?
There are many reasons, but mainly it comes down to value and choice...
When buying your chalcedony gemstone loose instead of a pre-set stone, you can be sure that you are getting the best value for your money. Loose gemstones are less expensive, a better value, and you can really see what you are paying for. The most important part of getting the right price and finding the best value is to first see what you're getting. A jewelry setting will hide the inclusions inside a gem, and can deepen or brighten its color. With a loose stone you can much more easily inspect the gem and see it for what it really is. In this way you can get a better idea of its true worth and be sure you are paying a fair price.
The second advantage of buying a loose gemstone is choice. You are free to pick the exact color, cut, shape and variety of the stone for the setting of your dreams, be it yellow gold, white gold, platinum or silver; prong set or bezel set with diamond accents. You can experience the joy of creating your very own, one-of-a-kind jewelry design. Choose from a variety of jewelry settings and styles to create a completely original presentation that will perfectly suit your individual gemstone and will be as unique as you are!
Attributes
| Origin |
Uruguay, India, Madagascar, Myanmar (Burma), Mexico Brazil, Southwestern Africa and across the U.S. |
| Color |
Blue-white, Africa Blue, Holly Blue, purple, buff, light tan, gray, yellow and brown |
| Refractive Index |
1.544 - 1.553 |
| Chemical Composition |
SiO2 |
| Hardness |
7 |
| Density |
2.6 - 2.7 |
| Crystal Structure |
Hexagonal |
| Zodiac Sign |
Libra |
"Chalcedony" is an umbrella term for a specific variety of quartz, or silicon dioxide, which comes in an assortment of sizes and colors. As a general rule, chalcedony is translucent to semi-transparent, and often has a milky or obscured color. It also takes well to polish, and some varieties of chalcedony seem to glow from within after prolonged polishing. The stone is typically classified by color, as chemically all chalcedony is identical. Popular examples of chalcedony include carnelian, agate, bloodstone, flint, and jasper, among many other stones.
The structure of chalcedony is classified as cryptocrystalline, meaning that the crystalline structure of the rock is so fine that it is not readily visible to the naked eye. In order to identify the individual crystals which make up chalcedony, it must be sliced into thin sections and viewed under a microscope with a polarized light source. Even then, the crystals are usually quite difficult to distinguish. This makes the stone relatively durable and easy to work with, far less prone to fracturing that other forms of quartz or minerals with larger crystal structures.
Some of the microcrystalline quartz varieties are: Amethyst, Ametrine, Cat's-eye Quartz, Citrine, Phantom Quartz , Rock Crystal, Rose Quartz, Rutilated Quartz and Smoky Quartz. Blue Aventurine Quartz and Green Aventurine Quartz are actually quartzites (a rock, not a mineral) composed essentially of interlocking macrocrystalline quartz grains with disseminated grains of other color imparting minerals.
The cryptocrystalline varieties of quartz may be separated into two types; fibrous and microgranular. Chalcedony is the general term applied to the fibrous cryptocrystalline varieties. Agate is an example of a fibrous cryptocystalline banded chalcedony variety of quartz. Carnelian, Chrysoprase and bloodstone are other chalcedony varieties.
Chert is the general term applied to the granular cryptocrystalline varieties of quartz, of which flint and Jasper are examples.
Chalcedony has a chemical formula of SiO2, a density of 2.60 - 2.70, and a refractive index of 1.544 - 1.553. The refractive index (RI), measured using a refractometer, is an indication of the amount light rays are bent by a mineral. Birefringence is the difference between the minimum and maximum RI. When birefringence is high, light rays reflect off different parts of the back of a stone causing an apparent doubling of the back facets when viewed through the front facet.
Most gems have a crystalline structure. Crystals have planes of symmetry and are divided into seven symmetry systems. The number of axes, their length, and their angle to each other determine the system to which a crystal belongs. Chalcedony gemstones belong to the Hexagonal crystal system.
Chalcedony is rated at 7 on Moh's Scale of hardness and is a tough, durable gem that is suitable for all jewelry applications, and easy to care for.
The colors are caused by trace amounts of other impurities in the silicon dioxide. Pure chalcedony without any trace minerals, often called milky quartz, is also found in some regions. Some types of chalcedony are more rare or sought after than other, causing costs to vary widely depending on the variety and the current market.
The various blues of chalcedony, each group of which has its vocal supporters, are generally designated by place names. They vary in depth of blue color and degree to which the blue is modified by gray or pink hues. As a group, they vary from pale to medium tones and in degree of translucency.
Some pieces have a slight adularescence that enhances their value. This phenomenon, which reaches its apex in moonstone, is due to light interference from layers of microscopic inclusions and looks like a shimmering, floating, interior light. Mohave and Mt. Airy Blues originate in California and Nevada, respectively and are slightly to moderately grayish blue with a light to medium color range. Blue chalcedony from Namibia, often called African Blue, varies from grayish to nearly pure blue and from light to medium dark. The most unusual type, and arguably the most valuable, is from Oregon. Its blues are modified by slight to moderate amounts of pink, making a noticeably lavender gem, which nonetheless is called "Holly Blue."
Chalcedony's beauty is enhanced when cut in cabochon shape. However, it can be given any shape or style. Common cuts are oval, square, round, pear etc. In modern jewelry this stone is used in new innovative shapes, made possible due to the stone's excellent durability.
Chalcedony is typically porous, so light colored chalcedony, in particular, can be dyed just about any color. Consequently, chalcedony has been dyed to resemble other gemrocks -- e.g., lapis lazuli -- and otherwise unmarketable chalcedony has even been dyed to the color of one of its desired varieties -- e.g., chrysoprase. Indeed, on occasion, some "off-colored" chalcedony has been bleached before dyeing it in order better to achieve the desired color. In addition, the color of some chalcedony has been changed by heating with the typical end product assuming a reddish hue.
Sosnagems fully discloses any and all treatments to our gemstones.
Chalcedony is finely crystallized or fibrous quartz found in sedimentary rocks during the volcanic eruption. It typically forms over a long period of time, as minerals are deposited into a pocket in another form of rock such as granite. Areas of volcanic activity frequently harbor deposits of chalcedony. Typically, the silicon dioxide forms parallel bands, which are sometimes readily visible, as is the case with many agates. In other cases, the separate deposits may appear blended to the eye, as with carnelians, moss agates, and many other forms of chalcedony.
Examples of chalcedony can be found all over the world, although some regions are better known than others for the production of high quality chalcedony. Almost all the states of United States produce this stone. Other countries are Uruguay, India, Madagascar, Myanmar (Burma), Mexico Brazil and Southwestern Africa.
The stone has been used for centuries in decorative art and jewelry, and often appears in the form of carved cameos, beads, or simple stone settings on rings, necklaces, and bracelets. Many societies associated particular traits with certain varieties of chalcedony, and many religious icons and symbols such as crosses, worry beads, and ornaments are made with various forms of chalcedony. It is also a popular choice of stone for many modern jewelers, who appreciate the range of colors and prices which chalcedony offers.
USA
All 50 States produce some variety of chalcedony, but the material from some States is better known than that from others.
Alaska -- The State has several varieties of chalcedony found at different locations, including agates, jaspers, and petrified wood. Various types of agates can be found in gravel pits and gravels of stream and river beds at several locations in the Chicken Creek area near the border with the Yukon Territory.
Agates, jasper, and petrified wood can be found on many beaches, including those on the islands of Adak, Admiralty, Attu, Kuiu, Kupreanof, Nelson, Popof, Tanaga, Unalaska, and Zarembo. These same materials can be found in the gravels or in many of the streams and rivers of the State. Other well known sources are the outlet of Becharof Lake, Little Nelchina River, and Caribou Creek.
Arizona -- Arizona is well known for its petrified wood because of the Petrified Forest National Park, and petrified wood ranks third in value of commercially produced gemstones. It is generally accepted that the Park contains the most colorful examples of silicified logs in the world.
Petrified wood occurs in every county in the State, but the commercial production is essentially from privately owned lands in Navajo and Apache Counties near the Petrified Forest. Federal regulations restrict collecting petrified wood on public lands to 250 pounds plus one piece per person per year, none of which is supposed to be sold commercially. The regulation essentially eliminates production from federal lands. Pieces as small as 1/4-inch to sections of logs 5 feet in diameter are recovered from the surface of the ground or with minimum excavations for use in the lapidary trade.
Arizona petrified wood has the broadest range of applications of any gem material produced in the State. The material is suitable for tumble polishing for use in baroque jewelry or for cutting into cabochons for jewelry and display. Freeform and calibrated slabs are polished for pen and pencil set bases and bases of other items, and polished slabs are used for clock faces. Additionally, large blocks, limb sections, and geometric shapes are used as bookends and decorator pieces. Objects of art, principally carvings, are produced, and furniture such as coffee and end tables are made from the petrified wood.
Arizona is the only State currently to have commercial production of fire agate. Fire agate is a form of chalcedony which contains inclusion of iron oxides that result in a play of colors much like that of precious opal. Eleven operations in Arizona report either commercial production of fire agate or dig-for-fee production. The material is produced in Graham, Greenlee, Maricopa, Mohave, and Yuma Counties.
Fire agate is cut into freeform and calibrated cabochons for use in the manufacture of silver and gold jewelry. The material is popular in the southwest and with hobbyist lapidaries throughout the United States. Fire agate also has been used and is currently used in Indian style jewelry.
California -- California's "Mojave Blue" agate has gained a great deal of attention in the past several years. This pastel blue or blue-gray agate cuts into attractive cabochons for jewelry and, in the hands of an expert carver, makes outstanding carvings.
Colorado and Utah -- These States have deposits of fine quality jasper, agate, petrified wood, and agatized dinosaur bone. These deposits are found over a large area of both States and on both sides of the continental divide in Colorado.
Florida--The famous silicified coral, first found in the Tampa Bay area around 1825 is the only gemstone of note from the State. Since its discovery in Tampa Bay, the agatized coral also has been found at Tarpon Springs, south of New Port Richey, near the town of Kathleen, and along the banks of the Suwanee River in Hamilton, Columbia, and Suwanee Counties. The material is found in two forms, as geodes, which represent partial replacement of coral, and as solid pieces which represent total replacement.
The coral is replaced by a waxy, translucent, botryoidal, varicolored chalcedony. The geodes are most often used as mineral specimens, but cabochon and tumbled gems can be made from the thin geode lining. The total replaced coral can be cut into attractive cabochons. The material can be blue, red, brown, amber, white, black, or a combination of these colors.
Idaho -- Jasper mining was beginning to make a comeback in the State, particularly with the operation of the Willow Creek jasper mine when in 1992, the untimely death of one of the partners mining the property, resulted in jasper mining reverting to hobbyist and professional collectors. Production of the various jaspers should be adequate to meet demand for the foreseeable future.
Montana -- Montana moss Agate is the grayish-white to gray translucent chalcedony containing dendrites. The black, brown, or red tree-like or scenic dendritic growths are actually included minerals of manganese and iron. Most of the moss agate is found as water worn cobbles in the Yellowstone River or its drainages between Billings and Sidney. The material can be collected in Yellowstone, Treasure, Rosebud, Custer, Prairie, Dawson, and Richland Counties. The agate has long been a favorite of hobbyist and professional cutters because of the beautiful and highly variable patterns, the durability, and ease in cutting and polishing.
New Mexico -- Varieties of agate, jasper, chert, or petrified wood are found in 15 of New Mexico's 32 counties. An area of about 100 hectares near Deming, New Mexico Rockhound State Park, is set aside for the non-commercial collecting of agate, jasper, and petrified wood.
Oregon -- The State is known for the production of various picture and scenic jaspers, agates, thundereggs, and petrified wood. Graveyard Point, Priday, and Polka Dot are names that are familiar to most agate collectors rockhounds, and many lapidaries. These are also names that are uniquely associated with Oregon and with beautiful agates. The same is true for the relationship between the names Biggs, Deschutes, and Sucker Creek and high quality picture or scenic jasper.
Oregon's State rock, the "thunderegg," may be the best known gem material from Oregon. Thundereggs were not, as believed by some people, ejected from volcanos, but formed in very soft and friable volcanic ash beds. Solutions containing silica permeated the cinders until favorable points for chalcedony deposition were achieved. Aggregations of chalcedony were deposited, but before the material could fully solidify the center of the concretion split apart, possibly because of shrinkage, permitting the later introduction of additional materials. The resulting star-shaped centers of chalcedony may be in the form of agate, jasper, or in some cases different varieties of opal.
Thundereggs are used in a number of ways. One of the most common uses is to simply saw the thunderegg into two pieces, polish the sawed face of each half, and use it as a display or decorative piece; bookends are also made in this fashion. Also, the thundereggs are sawed into slabs from which calibrated and freeform cabochons are cut. Additionally, at least one firm in the United States is manufacturing gem spheres from thundereggs.
South Dakota -- The State's best known chalcedony is its colorful and beautiful Fairburn agates. Named after a community near a very prolific agate deposit in Custer County, these brightly colored banded agates are similar to Lake Superior agates found in Michigan and Dryhead agates from Montana. The color patterns are alternating bands with one of the bands always white. The colors that alternate with white include yellowish-brown, dark red, salmon pink, black, yellow, grayish-blue, and milky-pink.
The agate nodules range in size from about 20 millimeters in diameter to some that weigh as much as 20 kilograms. The nodules are recovered from the weathering of the Chadron formation in an elongated belt covering parts of Custer, Pennington, and Shannon Counties, with the community of Fairburn at about the center of the belt. Nodules similar to the Fairburn nodules weather out of a limestone formation in an area that includes parts of Custer and Fall River Counties.
Other varieties of agate are found in the State. Moss agate, much like the famous Montana moss agate, can be found in river gravels of the Little Missouri River system in Harding County. A wide variety of agate can be found in the gravel pits in the entire eastern part of the State.
Tennessee -- Agates can be collected from many different locations and geological formations across the State. The material includes golden tone agate from Hawkins Co., agatized oolites from Greene Co., carnelian, blue, ivory, pink, finely banded, dendritic, moss, iris and Fairburn style agate from Bedford Co., and Lake Superior type agate and agatized corals and sponges from Shelby Co. All of the material is suitable for cutting and takes a good polish.
Texas -- Some of the best agate, jasper, chert, and petrified wood (particularly petrified palm wood) found in the nation comes from Texas. Blue banded, moss, and red and black plume agates are found near Alpine in Brewster County. Similar agates are found in Jeff Davis, Hidalgo, Hudspeth, Presidio, Reeves, San Patrico, and Starr Counties. Petrified wood can be found in Amarillo, Bastrop, Brazo, Comal, Duval, Fayette, Gonzales, Lavaca, and Uvalde Counties, with fine-quality palm wood coming from Live Oak and Webb Counties. Good-quality chert can be found in limestone formations in McCulloch, Moore, and San Saba Counties. The material from Moore County also is called Alibates flint and was used by prehistoric and modern-day Indians to make weapons and tools. The quarry from which the Indians obtained their flint is now Alibates State Park.
Washington -- Washington' s petrified woods are some of the finest in the nation. The woods not only represent a broad range of colors and patterns, but also represent a wide range of identifiable species. Species identified include redwood, oak (more than 10 varieties), cypress, elm, maple, willow, cedar, poplar, chestnut, alder, birch, persimmon, laurel, and ginkgo. The preserved woods have been used to make cabochons, table tops, pen bases, and other objects of art.
Deposits in the State also furnish a selection of agates that include moss, blue, and carnelian. The blue agate from Kittitas County, known as Ellensburg Blue, is highly prized by local lapidaries.
Wyoming -- Wyoming's claim to fame is its fine-quality agates and petrified wood. Deposits across the State supply a variety of seam, moss, banded, fortification, and turritella agates. Colorful and attractive specimens of petrified wood can be found in many areas in the State.
Others -- This is by no means a complete summary of chalcedony production in the United States. Flint from Flint Ridge, OH, and Lake Superior Agate from the Great Lakes were not discussed, nor was many other agates or jaspers from individuals favorite collecting locations. But in the space available, the better known or commercial producing locations were mentioned.
Chalcedony was a treasured gemstone of the ancient world. No important Roman would be without a seal, amulet or signet ring carved in this fine and durable material. The Victorians, too, prized chalcedony for carved cameos and intaglios: its fine texture allows for delicate and intricate workmanship.
Its name is derived from the name of the ancient Greek town known as Chalkedon in Asia Minor.
As early as the Bronze Age chalcedony was in use in the Mediterranean region; for example, on Minoan Crete at the Palace of Knossos chalcedony seals have been recovered dating to circa 1800 BC.
Chalcedony is believed to develop the emotional balance, stamina, kindness, generosity, responsiveness, receptivity, charity and friendliness.
Chalcedonies are believed to have been considered sacred stones by Native American Indians and they were often used for ceremonial purposes, particularly for promoting stability within the tribes.
In ancient times Chalcedony was used to heal physical problems like fever, leukemia, eye problems etc. It was believed to have the unique property of balancing the energy of the human body, mind, emotions and spirit.
Because there is little history about this precious and beautiful stone, most people usually look towards the two minerals present in Ametrine – Amethyst and Citrine. This means that Ametrine can relieve stress and make one feel calm. It can also make one enhance their thought process and mental capabilities.
