(likewise chosen a
semiprecious stone) is a piece of mineral crystal which, in cut and polished course, is used to brand jewelry or other adornments.[ane]
Withal, certain rocks (such as lapis lazuli, opal, and obsidian) and occasionally organic materials that are not minerals (such as amber, jet, and pearl) are besides used for jewelry and are therefore often considered to be gemstones every bit 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 and notoriety are other characteristics that lend value to gemstones.
Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem expert is a gemologist, a gem maker is called a lapidarist or gemcutter; a diamond cutter is chosen a diamantaire.
Characteristics and classification
The traditional nomenclature in the West, which goes back to the ancient Greeks, begins with a distinction between
semi-precious; similar distinctions are made in other cultures. In modern utilize, the precious stones are emerald, reddish, sapphire and diamond, with all other gemstones beingness semi-precious.[four]
This distinction reflects the rarity of the respective stones in ancient times, likewise every bit 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 modernistic values; for example, while garnets are relatively inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald.
Some other unscientific term for semi-precious gemstones used in art history and archeology is hardstone. Utilize of the terms ‘precious’ and ‘semi-precious’ in a commercial context is, arguably, misleading in that it deceptively implies sure stones are intrinsically more valuable than others, which is non necessarily the case.
In mod times gemstones are identified past gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The starting time characteristic a gemologist uses to identify a gemstone is its chemic composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al
). 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 precious stone is unremarkably establish in. For example, diamonds, which accept a cubic crystal organization, are frequently found as octahedrons.
Gemstones are classified into different
For example, ruby is the cherry-red variety of the species corundum, while whatever other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (carmine), goshenite (colorless), heliodor (xanthous), and morganite (pinkish), which are all varieties of the mineral species beryl.
Gems are characterized in terms of refractive alphabetize, 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 besides 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 “2d” or “third water” gems are those of a lesser transparency.[vii]
Gemstones have no universally accustomed grading organisation. 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 nevertheless graded using the naked eye (assuming 20/xx vision).
A mnemonic device, the “four Cs” (colour, cutting, clarity, and carats), has been introduced to help draw the factors used to grade a diamond.[ix]
With modification, these categories tin be useful in understanding the grading of all gemstones. The four criteria carry different weights depending upon whether they are applied to colored gemstones or to colorless diamonds. In diamonds, the cut is the primary determinant of value, followed past clarity and colour. The ideal cut diamond volition sparkle, to break down light into its constituent rainbow colors (dispersion), chop information technology upwards into bright niggling pieces (scintillation), and deliver it to the eye (luminescence). In its crude crystalline grade, a diamond will do none of these things; information technology requires proper fashioning and this is called “cut”. In gemstones that accept color, including colored diamonds, the purity, and beauty of that color is the chief determinant of quality.
Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds volition always take a number of inclusions), cut, unusual optical phenomena within the stone such as color zoning (the uneven distribution of coloring inside a jewel) and asteria (star effects). Aboriginal Greeks, for instance, greatly valued asteria gemstones, which they regarded as powerful love charms, and Helen of Troy was supposed to have worn star-corundum.
Bated from the diamond, cherry-red, sapphire, and emerald, the pearl (not, strictly speaking, a gemstone) and opal
have too been considered[
to exist precious. Upward to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a “precious stone” as well, going dorsum to ancient Greece. Fifty-fifty in the terminal century certain stones such equally aquamarine, peridot and cat’south middle (cymophane) take been pop and hence been regarded as precious.
Today the gemstone merchandise no longer makes such a distinction.
Many gemstones are used in even the most expensive jewelry, depending on the brand-proper name of the designer, fashion trends, market supply, treatments, etc. Nevertheless, diamonds, rubies, sapphires, and emeralds however take a reputation that exceeds those of other gemstones.[xiii]
Rare or unusual gemstones, mostly understood 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 in the quality of the rock. These characteristics include clarity, rarity, liberty from defects, the beauty of the rock, besides every bit the demand for such stones. In that location are different pricing influencers for both colored gemstones, and for diamonds. The pricing on colored stones is determined by market supply-and-demand, just diamonds are more intricate.
Diamond value can change based on location, time, and on the evaluations of diamond vendors.
Proponents of energy medicine too value gemstones on the basis of alleged healing powers.
There are a number of laboratories which course and provide reports on gemstones.
- Gemological Institute of America (GIA), the principal provider of education services and diamond grading reports
- International Gemological Institute (IGI), independent laboratory for grading and evaluation of diamonds, jewelry, and colored stones
- Hoge Raad Voor Diamant (HRD Antwerp), The Diamond High Council, Belgium is one of Europe’due south oldest laboratories; its main stakeholder is the Antwerp World Diamond Middle
- American Gemological Society (AGS) is not every bit widely recognized nor as onetime equally the GIA
- American Gem Trade Laboratory which is part of the American Precious stone Trade Association (AGTA), a merchandise organisation of jewelers and dealers of colored stones
- American Gemological Laboratories (AGL), owned by Christopher P. Smith
- European Gemological Laboratory (EGL), founded in 1974 by Guy Margel in Belgium
- Gemmological Association of All Japan (GAAJ-ZENHOKYO), Zenhokyo, Japan, active in gemological research
- The Precious stone and Jewelry Institute of Thailand (Public Organization) or GIT, Thailand’south national institute for gemological inquiry and gem testing, Bangkok
- Gemmology Constitute of Southern Africa, Africa’s premium gem laboratory
- Asian Establish of Gemological Sciences (AIGS), the oldest gemological establish in South East asia, involved in gemological pedagogy and gem testing
- Swiss Gemmological Plant (SSEF), founded past Henry Hänni, focusing on colored gemstones and the identification of natural pearls
- Gübelin Precious stone Lab, the traditional Swiss lab founded by Eduard Gübelin
- Institute for Gems and Gold Research of VINAGEMS (Vietnam), founded by Dr. Van Long Pham[
Each laboratory has its own methodology to evaluate gemstones. A stone tin be called “pink” by ane lab while another lab calls it “padparadscha”. One lab can conclude a stone is untreated, while another lab might conclude that it is estrus-treated.
To minimize 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 Transmission Harmonisation Commission (LMHC), for the standardization of diction reports, promotion of sure analytical methods and interpretation of results. Land 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 hard than determining other aspects of a gem (such as cut, clarity, etc.).
Another important new gemstone that has been ascent in popularity is Cuprian Elbaite Tourmaline which are also called “Paraiba Tourmaline”. Paraiba tourmaline were first discovered in early 1990 and recently in 2007 in Mozambique, Africa.[xx]
They are famous for their Glowing Neon Blue Color. Paraiba Tourmaline take become 1 of the most pop gemstones in recent times cheers to their unique color and recently considered to be one of the important gemstones after Carmine, Emerald and Sapphire co-ordinate to Gübelin Gemlab. Even though it is a tourmaline, paraiba are considered to be ane of the most expensive gemstones.
Gem dealers are aware of the differences betwixt gem laboratories and will make employ of the discrepancies to obtain the best possible document.
Cutting and polishing
A few gemstones are used as gems in the crystal or other forms in which they are found. Well-nigh, however, are cut and polished for usage as jewelry. The two principal classifications are stones cut as shine, dome-shaped stones called cabochons, and stones which are cut with a faceting motorcar by polishing small apartment windows called facets at regular intervals at exact angles.
Stones which are opaque or semi-opaque such as opal, turquoise, variscite, etc. are commonly cutting as cabochons. These gems are designed to testify the stone’s colour or surface properties equally in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and shine the shine dome shape of the stones.
Gems that are transparent are normally faceted, a method that shows the optical backdrop of the stone’southward interior to its best reward by maximizing reflected calorie-free which is perceived past the viewer equally 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 car is used to concur the stone onto a flat lap for cutting and polishing the apartment facets.
Rarely, some cutters use special curved laps to cutting and shine curved facets.
The color of whatever material is due to the nature of light itself. Daylight, often called white low-cal, is all of the colors of the spectrum combined. When light strikes a material, nigh of the lite is absorbed while a smaller amount of a item frequency or wavelength is reflected. The part that is reflected reaches the eye equally the perceived color. A cherry appears red because information technology absorbs all the other colors of white light while reflecting the red.
A cloth which is mostly the aforementioned tin exhibit different colors. For instance, ruby and sapphire have the same primary chemical limerick (both are corundum) but exhibit different colors considering of impurities. Even the same named gemstone can occur in many unlike colors: sapphires testify different shades of blue and pink and “fancy sapphires” exhibit a whole range of other colors from yellow to orangish-pink, the latter called “padparadscha sapphire”.
This departure in color is based on the diminutive structure of the stone. Although the different stones formally have the same chemical composition and construction, they are not exactly the same. Every at present and and so 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 exit the other colors unaffected.
For example, beryl, which is colorless in its pure mineral grade, 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 utilize of the fact that these impurities tin can exist “manipulated”, thus changing the color of the gem.
Gemstones are often treated to enhance the colour or clarity of the rock. Depending on the type and extent of treatment, they tin can bear on the value of the stone. Some treatments are used widely considering the resulting precious stone is stable, while others are not accustomed virtually usually because the gem color is unstable and may revert to the original tone.
Estrus tin can either better or spoil gemstone color or clarity. The heating procedure has been well known to gem miners and cutters for centuries, and in many rock types heating is a common practice. Most citrine is made past heating amethyst, and partial heating with a strong gradient results in “ametrine” – a stone partly amethyst and partly citrine. Aquamarine is frequently heated to remove yellow tones, or to modify green colors into the more desirable blue, or enhance its existing blue color to a deeper blueish.
Near all tanzanite is heated at low temperatures to remove dark-brown undertones and give a more desirable blue / purple colour.
A considerable portion of all sapphire and red is treated with a multifariousness of estrus treatments to meliorate both colour and clarity.
When jewelry containing diamonds is heated for repairs, the diamond should be protected with boric acrid; 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 exist coated with boric acid (which can etch the surface) or whatever other substance. They do not have to be protected from called-for, like a diamond (although the stones do need to be protected from heat stress fracture past immersing the part of the jewelry with stones in the h2o when metallic parts are heated).
Virtually all blue topaz, both the lighter and the darker blue shades such as “London” bluish, has been irradiated to alter the color from white to bluish. Most greened quartz (Oro Verde) is also irradiated to achieve the yellow-green color. Diamonds are irradiated to produce fancy-color diamonds (which can 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 improve color every bit well as clarity. Turquoise is also ordinarily treated in a similar manner.
Fracture filling has been in use with unlike gemstones such as diamonds, emeralds, and sapphires. In 2006 “glass-filled rubies” received publicity. Rubies over x carats (2 g) with big fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly piece of cake to observe.
Synthetic and bogus gemstones
Synthetic gemstones are distinct from imitation or simulated gems.
Synthetic gems are physically, optically, and chemically identical to the natural stone, just are created in a laboratory.
Faux or imitation stones are chemically different from the natural stone, simply may announced quite similar to it; they can be more than easily manufactured constructed gemstones of a different mineral (spinel), glass, plastic, resins, or other compounds.
Examples of faux or fake stones include cubic zirconia, composed of zirconium oxide, synthetic moissanite, and united nations-colored, synthetic corundum or spinels; all of which are diamond simulants. The simulants imitate the await and color of the existent stone but possess neither their chemical nor physical characteristics. In general, all are less hard than diamond. Moissanite actually has a
refractive alphabetize than diamond, and when presented beside an equivalently sized and cut diamond will show more “burn down”.
Cultured, synthetic, or “lab-created” gemstones are not imitations: The bulk mineral and trace coloring elements are the same in both. For example, diamonds, rubies, sapphires, and emeralds have been manufactured in labs that possess chemic and physical characteristics identical to the naturally occurring diverseness. Synthetic (lab created) corundum, including scarlet and sapphire, is very mutual and costs much less than the natural stones. Small synthetic diamonds accept been manufactured in large quantities as industrial abrasives, although larger gem-quality synthetic diamonds are condign available in multiple carats.
Whether a gemstone is a natural rock or synthetic, the chemic, physical, and optical characteristics are the aforementioned: They are equanimous of the same mineral and are colored past the same trace materials, have the same hardness and density and strength, and show the same color spectrum, refractive index, and birefringence (if any). Lab-created stones tend to have a more than bright color since impurities common in natural stones are non present in the synthetic stone. Synthetics are made complimentary of mutual naturally occurring impurities that reduce gem clarity or colour unless intentionally added in social club to provide a more drab, natural appearance, or to deceive an assayer.[
On the other hand, synthetics often show flaws not seen in natural stones, such equally infinitesimal particles of corroded metal from lab trays used during synthesis.
List of rare gemstones
- Painite was discovered in 1956 in Ohngaing in Myanmar. The mineral was named in honor of the British gemologist Arthur Charles Davy Pain. In 2005, painite was described by the Guinness Book of World Records as the rarest gem mineral on globe.
- Hibonite was discovered in 1956 in Madagascar. It was named later on the discoverer the French geologist Paul Hibon. Gem quality hibonite has been found only in Myanmar.
- Reddish beryl or bixbite was discovered in an area near Beaver, Utah in 1904 and named after the American mineralogist Maynard Bixby.
- Jeremejevite was discovered in 1883 in Russia and named afterwards its discoverer, Pawel Wladimirowich Jeremejew (1830–1899).
- Chambersite was discovered in 1957 in Chambers County, Texas, US, and named after the eolith’s location.
- Taaffeite was discovered in 1945. It was named later on the discoverer, the Irish gemologist Count Edward Charles Richard Taaffe.
- Musgravite was discovered in 1967 in the Musgrave Mountains in South Commonwealth of australia and named for the location.
- Grandidierite was discovered by Antoine François Alfred Lacroix (1863–1948) in 1902 in Tuléar Province, Madagascar. It was named in honor of the French naturalist and explorer Alfred Grandidier (1836–1912).
- Poudretteite was discovered in 1965 at the Poudrette Quarry in Canada and named after the quarry’s owners and operators, the Poudrette family unit.
- Serendibite was discovered in Sri Lanka by Sunil Palitha Gunasekera in 1902 and named after Serendib, the erstwhile Arabic proper noun for Sri Lanka.
- Zektzerite was discovered by Bart Cannon in 1968 on Kangaroo Ridge near Washington Pass in Okanogan Canton, Washington, United states of america. The mineral was named in honor of mathematician and geologist Jack Zektzer, who presented the material for report in 1976.
Run across also
- Assembled gem
- List of gemstone species
- List of gemstones
- Luminous gemstones
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Which Example Describes a Use for Gemstones