A gemstone (also called a gem, fine gem, jewel, precious stone, or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli and opal) and occasionally organic materials that are not minerals (such as amber, jet, and pearl) are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.
Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem maker is called a lapidary or gemcutter; a diamond cutter is called a diamantaire.
The traditional classification in the West, which goes back to the ancient Greeks, begins with a distinction between precious and semi-precious; similar distinctions are made in other cultures. In modern use the precious stones are diamond, ruby, sapphire and emerald, with all other gemstones being semi-precious. This distinction reflects the rarity of the respective stones in ancient times, as well as their quality: all are translucent with fine color in their purest forms, except for the colorless diamond, and very hard, with hardnesses of 8 to 10 on the Mohs scale. Other stones are classified by their color, translucency and hardness. The traditional distinction does not necessarily reflect modern values, for example, while garnets are relatively inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald. Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone. Use of the terms 'precious' and 'semi-precious' in a commercial context is, arguably, misleading in that it deceptively implies certain stones are intrinsically more valuable than others, which is not necessarily the case.
In modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al
3). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example, diamonds, which have a cubic crystal system, are often found as octahedrons.
Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow) and morganite (pink), which are all varieties of the mineral species beryl.
Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture and luster. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.
Material or flaws within a stone may be present as inclusions.
Gemstones may also be classified in terms of their "water". This is a recognized grading of the gem's luster, transparency, or "brilliance". Very transparent gems are considered "first water", while "second" or "third water" gems are those of a lesser transparency.
There is no universally accepted grading system for gemstones. Diamonds are graded using a system developed by the Gemological Institute of America (GIA) in the early 1950s. Historically, all gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision).
A mnemonic device, the "four Cs" (color, cut, clarity, and carats), has been introduced to help the consumer understand the factors used to grade a diamond. With modification, these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weight depending upon whether they are applied to colored gemstones or to colorless diamonds. In diamonds, cut is the primary determinant of value, followed by clarity and color. Diamonds are meant to sparkle, to break down light into its constituent rainbow colors (dispersion), chop it up into bright little pieces (scintillation), and deliver it to the eye (brilliance). In its rough crystalline form, a diamond will do none of these things; it requires proper fashioning and this is called "cut". In gemstones that have color, including colored diamonds, it is the purity and beauty of that color that is the primary determinant of quality.
Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds will always have a number of inclusions), cut, unusual optical phenomena within the stone such as color zoning (the uneven distribution of coloring within a gem) and asteria (star effects). The Greeks, for example, greatly valued asteria gemstones, which were regarded as powerful love charms, and Helen of Troy was known to have worn star-corundum.
Aside from the diamond, the ruby, sapphire, emerald, pearl (not, strictly speaking, a gemstone), and opal have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece. Even in the last century certain stones such as aquamarine, peridot and cat's eye (cymophane) have been popular and hence been regarded as precious.
Today such a distinction is no longer made by the gemstone trade. Many gemstones are used in even the most expensive jewelry, depending on the brand name of the designer, fashion trends, market supply, treatments, etc. Nevertheless, diamonds, rubies, sapphires, and emeralds still have a reputation that exceeds those of other gemstones.
Rare or unusual gemstones, generally meant to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and red beryl.
Gemstone pricing and value are governed by factors and characteristics on the quality of the stone. These characteristics include clarity, rarity, freedom of defects, beauty of the stone, as well as the demand for them. There are different pricing influencers for both colored gemstones, and for diamonds. The pricing on colored stones is determined by market supply-and-demand, but diamonds are more intricate. Diamond value can change based on location, time, and on the evaluations of diamond vendors.
There are a number of laboratories which grade and provide reports on gemstones.
Each laboratory has its own methodology to evaluate gemstones. A stone can be called "pink" by one lab while another lab calls it "padparadscha". One lab can conclude a stone is untreated, while another lab might conclude that it is heat-treated. To minimise such differences, seven of the most respected labs, AGTA-GTL (New York), CISGEM (Milano), GAAJ-ZENHOKYO (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), for the standardization of wording reports, promotion of certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to determine, due to the constant discovery of new source locations. Determining a "country of origin" is thus much more difficult than determining other aspects of a gem (such as cut, clarity, etc.).
Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate.
A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as jewelry. The picture to the left is of a rural, commercial cutting operation in Thailand. This small factory cuts thousands of carats of sapphire annually. The two main classifications are stones cut as smooth, dome shaped stones called cabochons, and stones which are cut with a faceting machine by polishing small flat windows called facets at regular intervals at exact angles.
Stones which are opaque or semi-opaque such as opal, turquoise, variscite, etc. are commonly cut as cabochons. These gems are designed to show the stone's color or surface properties as in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and polish the smooth dome shape of the stones.
Gems which are transparent are normally faceted, a method which shows the optical properties of the stone's interior to its best advantage by maximizing reflected light which is perceived by the viewer as sparkle. There are many commonly used shapes for faceted stones. The facets must be cut at the proper angles, which varies depending on the optical properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. The faceting machine is used to hold the stone onto a flat lap for cutting and polishing the flat facets. Rarely, some cutters use special curved laps to cut and polish curved facets.
The color of any material is due to the nature of light itself. Daylight, often called white light, is actually all of the colors of the spectrum combined. When light strikes a material, most of the light is absorbed while a smaller amount of a particular frequency or wavelength is reflected. The part that is reflected reaches the eye as the perceived color. A ruby appears red because it absorbs all the other colors of white light, while reflecting the red.
A material which is mostly the same can exhibit different colors. For example, ruby and sapphire have the same primary chemical composition (both are corundum) but exhibit different colors because of impurities. Even the same named gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "padparadscha sapphire".
This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition and structure, they are not exactly the same. Every now and then an atom is replaced by a completely different atom, sometimes as few as one in a million atoms. These so-called impurities are sufficient to absorb certain colors and leave the other colors unaffected.
For example, beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If manganese is added instead of chromium, beryl becomes pink morganite. With iron, it becomes aquamarine.
Some gemstone treatments make use of the fact that these impurities can be "manipulated", thus changing the color of the gem.
Gemstones are often treated to enhance the color or clarity of the stone. Depending on the type and extent of treatment, they can affect the value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone.
Heat can improve gemstone color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating is a common practice. Most citrine is made by heating amethyst, and partial heating with a strong gradient results in “ametrine” – a stone partly amethyst and partly citrine. Aquamarine is often heated to remove yellow tones, or to change green colors into the more desirable blue, or enhance its existing blue color to a purer blue.
Nearly all tanzanite is heated at low temperatures to remove brown undertones and give a more desirable blue / purple color. A considerable portion of all sapphire and ruby is treated with a variety of heat treatments to improve both color and clarity.
When jewelry containing diamonds is heated (for repairs) the diamond should be protected with boric acid; otherwise the diamond (which is pure carbon) could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies is heated, those stones should not be coated with boracic acid (which can etch the surface) or any other substance. They do not have to be protected from burning, like a diamond (although the stones do need to be protected from heat stress fracture by immersing the part of the jewelry with stones in water when metal parts are heated).
Virtually all blue topaz, both the lighter and the darker blue shades such as "London" blue, has been irradiated to change the color from white to blue. Most greened quartz (Oro Verde) is also irradiated to achieve the yellow-green color. Diamonds are irradiated to produce fancy-color diamonds (which occur naturally, though rarely in gem quality).
Emeralds containing natural fissures are sometimes filled with wax or oil to disguise them. This wax or oil is also colored to make the emerald appear of better color as well as clarity. Turquoise is also commonly treated in a similar manner.
Fracture filling has been in use with different gemstones such as diamonds, emeralds and sapphires. In 2006 "glass filled rubies" received publicity. Rubies over 10 carats (2 g) with large fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly easy to detect.
It is important to distinguish between synthetic gemstones, and imitation or simulated gems.
Synthetic gems are physically, optically and chemically identical to the natural stone, but are created in controlled conditions in a laboratory. Imitation or simulated stones are chemically different from the natural stone but may be optically similar to it; they can be glass, plastic, resins or other compounds.
Examples of simulated or imitation stones include cubic zirconia, composed of zirconium oxide and simulated moissanite, which are both diamond simulants. The imitations copy the look and color of the real stone but possess neither their chemical nor physical characteristics. Moissanite actually has a higher refractive index than diamond and when presented beside an equivalently sized and cut diamond will have more "fire" than the diamond.
Synthetic, cultured or lab-created gemstones are not imitations. For example, diamonds, rubies, sapphires and emeralds have been manufactured in labs to possess identical chemical and physical characteristics to the naturally occurring variety. Synthetic (lab created) corundum, including ruby and sapphire, is very common and costs much less than the natural stones. Smaller synthetic diamonds have been manufactured in large quantities as industrial abrasives, although larger gem-quality synthetic diamonds are becoming available in multiple carats.
Whether a gemstone is a natural stone or lab-created (synthetic), the physical characteristics are the same. Lab-created stones tend to have a more vivid color to them, as impurities are not present in a lab and do not modify the clarity or color of the stone, unless added intentionally for a specific purpose.
Ammolite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral contained in nacre, with a microstructure inherited from the shell. It is one of few biogenic gemstones; others include amber and pearl.1 In 1981, ammolite was given official gemstone status by the World Jewellery Confederation (CIBJO), the same year commercial mining of ammolite began. It was designated the official gemstone of the City of Lethbridge, Alberta in 2007.Ammolite is also known as aapoak (Kainah for "small, crawling stone"), gem ammonite, calcentine, and Korite. The latter is a trade name given to the gemstone by the Alberta-based mining company Korite. Marcel Charbonneau and his business partner Mike Berisoff were the first to create commercial doublets of the gem in 1967. They went on to form Ammolite Minerals Ltd.Beryl
Beryl ( BERR-əl) is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red (the rarest), and white. Beryl is also an ore source of beryllium.Cameo (carving)
Cameo () is a method of carving an object such as an engraved gem, item of jewellery or vessel. It nearly always features a raised (positive) relief image; contrast with intaglio, which has a negative image. Originally, and still in discussing historical work, cameo only referred to works where the relief image was of a contrasting colour to the background; this was achieved by carefully carving a piece of material with a flat plane where two contrasting colours met, removing all the first colour except for the image to leave a contrasting background.
A variation of a carved cameo is a cameo incrustation (or sulphide). An artist, usually an engraver, carves a small portrait, then makes a cast from the carving, from which a ceramic type cameo is produced. This is then encased in a glass object, often a paperweight. These are very difficult to make but were popular from the late 18th century through the end of the 19th century. Originating in Bohemia, the finest examples were made by the French glassworks in the early to mid-nineteenth century.Today the term may be used very loosely for objects with no colour contrast, and other, metaphorical, terms have developed, such as cameo appearance. This derives from another generalized meaning that has developed, the cameo as an image of a head in an oval frame in any medium, such as a photograph.Carat (mass)
The carat (ct) (not to be confused with the unit of purity of gold alloys, which is also spelled carat in UK English but usually spelled karat in US English), is a unit of mass equal to 200 mg (0.2 g; 0.007055 oz) and is used for measuring gemstones and pearls.
The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world. The carat is divisible into one hundred points of two milligrams each. Other subdivisions, and slightly different mass values, have been used in the past in different locations.
In terms of diamonds, a paragon is a flawless stone of at least 100 carats (20 g).The ANSI X.12 EDI standard abbreviation for the carat is CD.Diamond (gemstone)
A diamond (from the Ancient Greek: ἀδάμας adámas, meaning "unbreakable", "proper", or "unalterable") is one of the best-known and most sought-after gemstones. Diamonds have been used as decorative items since ancient times; some of the earliest references can be traced to 25,000 - 30,000 B.C.
The hardness of diamond and its high dispersion of light—giving the diamond its characteristic "fire"—make it useful for industrial applications and desirable as jewelry. Diamonds are such a highly traded commodity that multiple organizations have been created for grading and certifying them based on the "four Cs", which are color, cut, clarity, and carat. Other characteristics, such as presence or lack of fluorescence, also affect the desirability and thus the value of a diamond used for jewelry.
Diamonds are used in engagement rings. The practice is documented among European aristocracy as early as the 15th century, though ruby and sapphire were more desirable gemstones. The modern popularity of diamonds was largely created by De Beers Consolidated Mines Ltd., which established the first large-scale diamonds mines in South Africa. Through an advertising campaign beginning in the 1930s and continuing into the mid-20th century, De Beers made diamonds into a key part of the betrothal process and a coveted symbol of status. The diamond's high value has been the driving force behind dictators and revolutionary entities, especially in Africa, using slave and child labor to mine blood diamonds to fund conflicts. Though popularly believed to derive its value from its rarity, gem-quality diamonds are quite common compared to rare gemstones such as alexandrite, and annual global rough diamond production is estimated to be about 130 million carats (26 tonnes; 29 short tons).Diamond Comic Distributors
Diamond Comic Distributors, Inc. (often called Diamond Comics, DCD, or casually Diamond) is a comic book distributor serving retailers in North America and worldwide. They transport comic books and graphic novels from both big and small comic book publishers, or suppliers, to retailers, as well as other pop-culture products such as toys, games, and apparel. Diamond distributes to the direct market in the United States, and has an exclusive distribution arrangements with most major U.S. comic book publishers, including Dark Horse Comics, DC Comics, IDW Publishing, Image Comics, Marvel Comics, and more.
Diamond is also the parent company of Alliance Game Distributors, Diamond Book Distributors, Diamond UK, Diamond Select Toys, Gemstone Publishing, E. Gerber Products, Diamond International Galleries, Hake's Americana & Collectibles, Morphy's Auctions, the Geppi's Entertainment Museum, and Baltimore magazine,
Diamond is the publisher of Previews, a monthly catalog/magazine showcasing upcoming comic books, graphic novels, toys, and other pop-culture merchandise available at comic book specialty shops. The publication is available to both comic shop retailers and consumers.Garnet
Garnets ( ) are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different species are pyrope, almandine, spessartine, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite. The garnets make up two solid solution series: pyrope-almandine-spessartine and uvarovite-grossular-andradite.Gemology
Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.Gemstone Publishing
Gemstone Publishing is an American company that publishes comic book price guides. The company was formed by Diamond Comic Distributors President and Chief Executive Officer Steve Geppi in 1994 when he bought Overstreet.Gemstone published licensed Disney comic books from June 2003 until November 2008. The company has also reprinted EC Comics of the 1950s.
BOOM! Kids acquired all comic publishing licenses regarding Disney characters in the second half of 2009.Inclusion (mineral)
In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.
In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior.
According to Hutton's law of inclusions, fragments included in a host rock are older than the host rock itself.List of U.S. state minerals, rocks, stones and gemstones
Leaders of states in the U.S. which have significant mineral deposits often create a state mineral, rock, stone or gemstone to promote interest in their natural resources, history, tourism, etc. Not every state has an official state mineral, rock, stone and/or gemstone, however.
In the chart below, a year which is listed within parentheses represents the year during which that mineral, rock, stone or gemstone was officially adopted as a state symbol or emblem.Moonstone (gemstone)
Moonstone is a sodium potassium aluminium silicate ((Na,K)AlSi3O8) of the feldspar group that displays a pearly and opalescent schiller. An alternative name is hecatolite.Precious coral
Precious coral, or red coral, is the common name given to a genus of marine corals, Corallium. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink-orange skeleton, which is used for making jewelry.Quartz
Quartz is a mineral composed of silicon and oxygen atoms in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C (846 K). Since the transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature threshold.
There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia.Ruby
A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, together with amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.
Some gemstones that are popularly or historically called rubies, such as the Black Prince's Ruby in the British Imperial State Crown, are actually spinels. These were once known as "Balas rubies".
The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red called blood-red or pigeon blood, commands a large premium over other rubies of similar quality. After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Ruby is the traditional birthstone for July and is usually pinker than garnet, although some rhodolite garnets have a similar pinkish hue to most rubies. The world's most valuable ruby is the Sunrise Ruby.Simutronics
Simutronics is an American online games company whose products include GemStone IV and DragonRealms. It was founded in 1987 by David Whatley, with husband and wife Tom & Susan Zelinski. The company is located in St. Louis, Missouri. It became part of the Stillfront Group in 2016.
The company's flagship product is the text based game, GemStone IV, which went live in November 2003, with predecessor games running back to 1988. GemStone was originally accessed through General Electric's internet service provider GEnie, later becoming accessible through AOL, Prodigy, and CompuServe before Simutronics finally moved all their games to their own domain in 1997.The Righteous Gemstones
The Righteous Gemstones is an upcoming American comedy television series, created by Danny McBride, that is set to premiere in 2019 on HBO. The series follows a famous yet dysfunctional family of televangelists and stars McBride, John Goodman, Edi Patterson, Adam DeVine, Cassidy Freeman, Tony Cavalero, and Tim Baltz.Topaz
Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F, OH)2. Topaz crystallizes in the orthorhombic system, and its crystals are mostly prismatic terminated by pyramidal and other faces. It is one of the hardest naturally occurring minerals (Mohs hardness of 8) and is the hardest of any silicate mineral. This hardness combined with its usual transparency and variety of colors means that it has acquired wide use in jewellery as a cut gemstone as well as for intaglios and other gemstone carvings.Wedding anniversary
A wedding anniversary is the anniversary of the date a wedding took place. Traditional names exist for some of them: for instance, fifty years of marriage is called a "golden wedding anniversary" or simply a "golden anniversary" or "golden wedding".
Gemmological Classifiactions by E. Ya. Kievlenko, 1980, updated