Gemstone

Last updated

Group of precious and semiprecious stones--both uncut and faceted--including (clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster. Cardinal gems.png
Group of precious and semiprecious stones—both uncut and faceted—including (clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster.

A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments. [1] [2] [3] Certain rocks (such as lapis lazuli, opal, and obsidian) and occasionally organic materials that are not minerals (such as amber, jet, and pearl) may also be used for jewelry and are therefore often considered to be gemstones as well. [4] [5] Most gemstones are hard, but some softer minerals such as brazilianite may be used in jewelry [6] because of their color or luster or other physical properties that have aesthetic value. However, generally speaking, soft minerals are not typically used as gemstones by virtue of their brittleness and lack of durability. [7]

Contents

Found all over the world, the industry of coloured gemstones (i.e. anything other than diamonds) is currently estimated at US$1.55 billion as of 2023 and is projected to steadily increase to a value of US$4.46 billion by 2033. [8]

A gem expert is a gemologist, a gem maker is called a lapidarist or gemcutter; a diamond cutter is called a diamantaire.

Characteristics and classification

A collection of gemstone pebbles made by tumbling the rough stones, except the ruby and tourmaline, with abrasive grit inside a rotating barrel. The largest pebble here is 40 mm (1.6 in) long. Gem.pebbles.800pix.labelled.jpg
A collection of gemstone pebbles made by tumbling the rough stones, except the ruby and tourmaline, with abrasive grit inside a rotating barrel. The largest pebble here is 40 mm (1.6 in) long.

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 emerald, ruby, sapphire and diamond, with all other gemstones being semi-precious. [9] 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 a hardness score of 8 to 10 on the Mohs scale. [10] 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. [11] Another traditional 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 suggests certain stones are more valuable than others when this is not reflected in the actual market value, although it would generally be correct if referring to desirability.

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
2O
3). 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. [12] For example, diamonds, which have a cubic crystal system, are often found as octahedrons. [13]

Gemstones are classified into different groups, species, and varieties. [14] [15] 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 their color (hue, tone and saturation), optical phenomena, luster, refractive index, birefringence, dispersion, specific gravity, hardness, cleavage, and fracture. [16] [17] They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum. Gemstones may also be classified in terms of their "water". This is a recognized grading of the gem's luster, transparency, or "brilliance". [18] Very transparent gems are considered "first water", while "second" or "third water" gems are those of a lesser transparency. [19] Additionally, material or flaws within a stone may be present as inclusions. [20]

Value

Spanish emerald and gold pendant at Victoria and Albert Museum Spanish jewellery-Gold and emerald pendant at VAM-01.jpg
Spanish emerald and gold pendant at Victoria and Albert Museum
Enamelled gold, amethyst, and pearl pendant, about 1880, Pasquale Novissimo (1844-1914), V&A Museum number M.36-1928 Pendant (cropped).jpg
Enamelled gold, amethyst, and pearl pendant, about 1880, Pasquale Novissimo (1844–1914), V&A Museum number M.36-1928

Gemstones have no universally accepted grading system. 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). [21]

A mnemonic device, the "four Cs" (color, cut, clarity, and carats), has been introduced to help describe 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 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 by clarity and color. An ideally cut diamond will 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, the purity, and beauty of that color is the primary determinant of quality. [22]

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) [23] and asteria (star effects).

Apart from the more generic and commonly used gemstones such as from diamonds, rubies, sapphires, and emeralds, pearls and opal [24] have also been defined as precious in the jewellery trade. 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, thus reinforcing the notion that a mineral's rarity may have been implicated in its classification as a precious stone and thus contribute to its value.

Today the gemstone trade no longer makes such a distinction. [25] 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. [26]

Rare or unusual gemstones, generally 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, painite and red beryl. [27]

Gemstone pricing and value are governed by factors and characteristics in the quality of the stone. These characteristics include clarity, rarity, freedom from defects, the beauty of the stone, as well as the demand for such stones. 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. [28]

In the addition to the aesthetic and adorning/ornamental purpose of gemstones, there are many proponents of energy medicine who also value gemstones on the basis of their alleged healing powers. [29]

A gemstone that has been rising in popularity is Cuprian Elbaite Tourmaline which is also called "Paraiba Tourmaline". It was first discovered in the late 1980s in Paraíba, Brazil and later in Mozambique and Nigeria. [30] It is famous for its glowing neon blue color. Paraiba Tourmaline has become one of the most popular gemstones in recent times thanks to its color and is considered to be one of the important gemstones after rubies, emeralds, and sapphires according to Gübelin Gemlab. Even though it is a tourmaline, Paraiba Tourmaline is one of the most expensive gemstones. [31]

Grading

There are a number of laboratories which grade and provide reports on gemstones. [25]

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. [25] 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 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.). [33]

Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate. [25]

Cutting and polishing

A diamond cutter in Amsterdam Diamond cutter. Amsterdam. 2012.jpg
A diamond cutter in Amsterdam

A few gemstones are used as gems in the crystal or other forms in which they are found. Most, however, are cut and polished for usage as jewelry. The two main classifications are as follows:

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, luster and other surface properties as opposed to internal reflection properties like brilliance. [34] Grinding wheels and polishing agents are used to grind, shape, and polish the smooth dome shape of the stones. [35]

Gems that are transparent are normally faceted, a method that 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. [36] Rarely, some cutters use special curved laps to cut and polish curved facets.

Colors

Nearly 300 variations of diamond color exhibited at the Aurora display at the Natural History Museum in London Aurora Pyramid of Hope.jpg
Nearly 300 variations of diamond color exhibited at the Aurora display at the Natural History Museum in London
A variety of semiprecious stones in a piece of jewellery Semiprecious stones in a piece of jewellery.jpeg
A variety of semiprecious stones in a piece of jewellery

The color of any material is due to the nature of light itself. Daylight, often called white light, is 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. [37] A ruby appears red because it absorbs all other colors of white light while reflecting 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) [38] but exhibit different colors because of impurities which absorb and reflect different wavelengths of light depending on their individual compositions. 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". [39]

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.

Treatment

Gemstones are often treated to enhance the color or clarity of the stone. [40] In some cases, the treatment applied to the gemstone can also increase its durability. Even though natural gemstones can be transformed using the traditional method of cutting and polishing, other treatment options allow the stone's appearance to be enhanced. [41] 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. [42]

Early history

Before the innovation of modern-day tools, thousands of years ago, people were recorded to use a variety of techniques to treat and enhance gemstones. Some of the earliest methods of gemstone treatment date back to the Minoan Age, for example foiling, which is where metal foil is used to enhance a gemstone's colour. [43] Other methods recorded 2000 years ago in the book Natural History by Pliny the Elder include oiling and dyeing/staining.

Heat

Heat can either improve or spoil 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 deeper blue. [42]

Nearly all tanzanite is heated at low temperatures to remove brown undertones and give a more desirable blue / purple color. [44] 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 boric 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 the water when metal parts are heated).

Radiation

The irradiation process is widely practiced in jewelry industry [45] and enabled the creation of gemstone colors that do not exist or are extremely rare in nature. [46] However, particularly when done in a nuclear reactor, the processes can make gemstones radioactive. Health risks related to the residual radioactivity of the treated gemstones have led to government regulations in many countries. [46] [47]

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 green quartz (Oro Verde) are also irradiated to achieve the yellow-green color. Diamonds are mainly irradiated to become blue-green or green, although other colors are possible. When light-to-medium-yellow diamonds are treated with gamma rays they may become green; with a high-energy electron beam, blue. [48]

Waxing/oiling

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

The foreign material inside this fracture-filled emerald appears rainbow-colored under darkfield illumination. Emerald Fracture Filled Rainbow.jpg
The foreign material inside this fracture-filled emerald appears rainbow-colored under darkfield illumination.

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.

Bleaching

Pearls are a gemstone that is commonly treated with hydrogen peroxide to remove unwanted colours Pearl from Pinctada maxima (gold-lipped pearl oyster) 1.jpg
Pearls are a gemstone that is commonly treated with hydrogen peroxide to remove unwanted colours

Another treatment method that is commonly used to treat gemstones is bleaching. This method uses a chemical in order to reduce the colour of the gem. After bleaching, a combination treatment can be done by dying the gemstone once the unwanted colours are removed. Hydrogen peroxide is the most commonly used product used to alter gemstones and have notably been used to treat jade and pearls. The treatment of bleaching can also be followed by impregnation, which allows the gemstone's durability to be increased. [41]

Socioeconomic issues in the gemstone industry

The socio-economic dynamics of the gemstone industry are shaped by market forces and consumer preferences and typically go undiscussed. Changes in demand and prices can significantly affect the livelihoods of those involved in gemstone mining and trade, particularly in developing countries where the industry serves as a crucial source of income. [49]

A situation that arises as a result of this is the exploitation of natural resources and labor within gemstone mining operations. Many mines, particularly in developing countries, face challenges such as inadequate safety measures, low wages, and poor working conditions. [49] Miners, often from disadvantaged backgrounds, endure hazardous working conditions and receive meager wages, contributing to cycles of poverty and exploitation. [50] Gemstone mining operations are frequently conducted in remote or underdeveloped areas, lacking proper infrastructure and access to essential services such as healthcare and education. This further contributes to the pre-existing socio-economic disparities and obstructs community development such that the benefits of gemstone extraction may not adequately reach those directly involved in the process. [51]

Another such issue revolves around environmental degradation resulting from mining activities. Environmental degradation can pose long-term threats to ecosystems and biodiversity, further worsening the socio-economic state in affected regions. [52] Unregulated mining practices often result in deforestation, soil erosion, and water contamination thus threatening ecosystems and biodiversity. [53] Unregulated mining activity can also cause depletion of natural resources, thus diminishing the prospects for sustainable development. [54] The environmental impact of gemstone mining not only poses a threat to ecosystems but also undermines the long-term viability of the industry by diminishing the quality and quantity of available resources.

Furthermore, the gemstone industry is also susceptible to issues related to transparency and ethics, which impact both producers and consumers. The lack of standardized certification processes and the prevalence of illicit practices undermine market integrity and trust. [55] The lack of transparency and accountability in the supply chain aggravates pre-existing inequalities, as middlemen and corporations often capture a disproportionate share of the profits. As a result, the unequal distribution of profits along the supply chain does little to improve socio-economic inequalities, particularly in regions where gemstones are mined.

Addressing these socio-economic challenges requires intensive effort from various stakeholders, including governments, industry executives, and society, to promote sustainable practices and ensure equitable outcomes for all involved parties. Implementing and enforcing regulations to ensure fair labor practices, environmental sustainability, and ethical sourcing is essential. Additionally, investing in community development projects, such as education and healthcare initiatives, can help alleviate poverty and empower marginalized communities dependent on the gemstone industry. Collaboration across sectors is crucial for fostering a more equitable and sustainable gemstone trade that benefits both producers and consumers while respecting human rights and environmental integrity.

Synthetic and artificial gemstones

Synthetic gemstones are distinct from imitation or simulated gems.

Synthetic gems are physically, optically, and chemically identical to the natural stone, but are created in a laboratory. [56] Imitation or simulated stones are chemically different from the natural stone, but may appear quite similar to it; they can be more easily manufactured synthetic gemstones of a different mineral (spinel), glass, plastic, resins, or other compounds.

Examples of simulated or imitation stones include cubic zirconia, composed of zirconium oxide, synthetic moissanite, and uncolored, synthetic corundum or spinels; all of which are diamond simulants. The simulants imitate the look and color of the real stone but possess neither their chemical nor physical characteristics. In general, all are less hard than diamond. Moissanite actually has a higher refractive index than diamond, and when presented beside an equivalently sized and cut diamond will show more "fire".

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 chemical and physical characteristics identical to the naturally occurring variety. Synthetic (lab created) corundum, including ruby and sapphire, is very common and costs much less than the natural stones. Small synthetic diamonds have been manufactured in large quantities as industrial abrasives, although larger gem-quality synthetic diamonds are becoming available in multiple carats. [57]

Whether a gemstone is a natural stone or synthetic, the chemical, physical, and optical characteristics are the same: They are composed of the same mineral and are colored by 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 vivid color since impurities common in natural stones are not present in the synthetic stone. Synthetics are made free of common naturally occurring impurities that reduce gem clarity or color unless intentionally added in order to provide a more drab, natural appearance, or to deceive an assayer.[ citation needed ] On the other hand, synthetics often show flaws not seen in natural stones, such as minute particles of corroded metal from lab trays used during synthesis.[ citation needed ]

Types

Some gemstones are more difficult to synthesize than others and not all stones are commercially viable to attempt to synthesize. These are the most common on the market currently. [58]

Synthetic corundum

Synthetic corundum includes ruby (red variation) and sapphire (other color variations), both of which are considered highly desired and valued. [58] Ruby was the first gemstone to be synthesized by Auguste Verneuil with his development of the flame-fusion process in 1902. [59] Synthetic corundum continues to be made typically by flame-fusion as it is most cost-effective, but can also be produced through flux growth and hydrothermal growth. [60]

Synthetic beryls

The most common synthesized beryl is emerald (green). Yellow, red and blue beryls are possible but much more rare. Synthetic emerald became possible with the development of the flux growth process and is produced in this way and well as hydrothermal growth. [61]

Synthetic quartz

Types of synthetic quartz include citrine, rose quartz, and amethyst. Natural occurring quartz is not rare, but is nevertheless synthetically produced as it has practical application outside of aesthetic purposes. Quartz generates an electric current when under pressure and is used in watches, clocks, and oscillators. [62]

Synthetic spinel

Synthetic spinel was first produced by accident.[ clarification needed ] It can be created in any color making it popular to simulate various natural gemstones. It is created through flux growth and hydrothermal growth. [58]

Creation process

There are two main categories for creation of these minerals: melt or solution processes. [58]

Verneuil flame fusion process (melt process)

Verneuil furnace Verneuil process diagram.svg
Verneuil furnace

The flame fusion process was the first process used which successfully created large quantities of synthetic gemstones to be sold on the market. [63] This remains the most cost effective and common method of creating corundums today.

The flame fusion process is completed in a Verneuil furnace. The furnace consists of an inverted blowpipe burner which produces an extremely hot oxyhydrogen flame, a powder dispenser, and a ceramic pedestal. [64] A chemical powder which corresponds to the desired gemstone is passed through this flames. This melts the ingredients which drop on to a plate and solidify into a crystal called a boule. [64] For corundum the flame must be 2000 °C. This process takes hours and yields a crystal with the same properties as its natural counterpart.

To produce corundum, a pure aluminium powder is used with different additives to achieve different colors. [64]

  • Chromic oxide for ruby
  • Iron and titanium oxide for blue sapphire
  • Nickel oxide for yellow sapphire
  • Nickel, chromium and iron for orange sapphire
  • Manganese for pink sapphire
  • Copper for blue-green sapphire
  • Cobalt for dark blue sapphire

Czochralski process (melt process)

In 1918 this process was developed by J. Czocharalski [64] and is also referred to as the "crystal pulling" method. In this process, the required gemstone materials are added to a crucible. A seed stone is placed into the melt in the crucible. As the gem begins to crystallize on the seed, the seed is pulled away and the gem continues to grow. [58] This is used for corundum but is currently the least popular method. [63]

Flux growth (solution process)

The flux growth process was the first process able to synthesize emerald. [61] Flux growth begins with a crucible which can withstand high heat; either graphite or platinum which is filled with a molten liquid referred to as flux. [65] The specific gem ingredients are added and dissolved in this fluid and recrystallize to form the desired gemstone.This is a longer process compared to the flame fusion process and can take two months up to a year depending on the desired final size. [66]

Hydrothermal growth (solution process)

The hydrothermal growth process attempts to imitate the natural growth process of minerals. The required gem materials are sealed in a container of water and placed under extreme pressure. The water is heated beyond its boiling point which allows normally insoluble materials to dissolve. As more material cannot be added once the container is sealed, in order to create a larger gem the process would begin with a "seed" stone from a previous batch which the new material will crystallize on. This process takes a few weeks to complete.

Characteristics

Synthetic gemstones share chemical and physical properties with natural gemstones, but there are some slight differences that can be used to discern synthetic from natural. [67] These differences are slight and often require microscopy as a tool to distinguish differences. Undetectable synthetics pose a threat to the market if they are able to be sold as rare natural gemstones.[ citation needed ] Because of this there are certain characteristic gemologists look for. Each crystal is characteristic to the environment and growth process under which it was created.

Visible banding in an apatite gemstone Golden Apatite.jpg
Visible banding in an apatite gemstone

Gemstones created from the flame-fusion process may have

Gemstones created from flux melt process may have

Gemstones created from hydrothermal growth may have

History

Auguste Verneuil - creator of flame-fusion process 1902 Auguste Victor Louis Verneuil.jpg
Auguste Verneuil – creator of flame-fusion process 1902

Prior to development of synthesising processes the alternatives on the market to natural gemstones were imitations or fake. In 1837, the first successful synthesis of ruby occurred. [63] French chemist Marc Gaudin managed to produce small crystals of ruby from melting together potassium aluminium sulphate and potassium chromate through what would later be known as the flux melt process. [64] Following this, another French chemist Fremy was able to grow large quantities of small ruby crystals using a lead flux. [65]

A few years later an alternative to flux melt was developed which led to the introduction of what was labeled "reconstructed ruby" to the market. Reconstructed ruby was sold as a process which produced larger rubies from melting together bits of natural ruby. [66] In later attempts to recreate this process it was found to not be possible and is believed reconstructed rubies were most likely created using a multi-step method of melting of ruby powder. [64]

Auguste Verneuil, a student of Fremy, went on to develop flame-fusion as an alternative to the flux-melt method. He developed large furnaces which were able to produce large quantities of corundums more efficiently and shifted the gemstone market dramatically. [69] This process is still used today and the furnaces have not changed much from the original design. [70] World production of corundum using this method reaches 1000 million carats a year.

List of rare gemstones

Red Beryl - discovered in 1940 RedBeryl-G-EmpireTheWorldOfGems (cropped).jpg
Red Beryl - discovered in 1940
Black Opal - the rarest type of opal Black opal (Stayish Mine, Wollo Province, Ethiopia) 6 (23226115484).jpg
Black Opal – the rarest type of opal

French singer-songwriter Nolwenn Leroy was inspired by the gemstones for her 2017 album Gemme (meaning gemstone in French) and the single of the same name. [74]

See also

Related Research Articles

<span class="mw-page-title-main">Amethyst</span> Mineral, quartz variety

Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α-a-, "not" and μεθύσκωmethysko / μεθώmetho, "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.

<span class="mw-page-title-main">Beryl</span> Gemstone: beryllium aluminium silicate

Beryl ( BERR-əl) is a mineral composed of beryllium aluminium silicate 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, pink, and red (the rarest). It is an ore source of beryllium.

<span class="mw-page-title-main">Corundum</span> Oxide mineral

Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium, and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange.

<span class="mw-page-title-main">Emerald</span> Green gemstone, a beryl variety

Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds have many inclusions, so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.

<span class="mw-page-title-main">Sapphire</span> Gem variety of corundum

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name sapphire is derived from the Latin word sapphirus, itself from the Greek word sappheiros (σάπφειρος), which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on the locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third-hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

<span class="mw-page-title-main">Topaz</span> Silicate mineral

Topaz is a silicate mineral made of aluminum and fluorine with the chemical formula Al2SiO4(F, OH)2. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow-orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.

<span class="mw-page-title-main">Ruby</span> Variety of corundum, mineral, gemstone

Ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside 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.

<span class="mw-page-title-main">Chrysoberyl</span> Mineral or gemstone of beryllium aluminate

The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones, although they both contain beryllium. Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the Mohs scale of mineral hardness, between corundum (9) and topaz (8).

<span class="mw-page-title-main">Gemology</span> Science dealing with natural and artificial gemstone materials

Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is a specific interdisciplinary branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.

Diamond clarity is the quality of diamonds that relates to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects, called blemishes. Clarity is one of the four Cs of diamond grading, the others being carat, color, and cut.

<span class="mw-page-title-main">Diamond simulant</span> Diamond-like object which is not a diamond

A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds, which are actual diamonds exhibiting the same material properties as natural diamonds. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection.

<span class="mw-page-title-main">Gemological Institute of America</span> Research institute in Carlsbad, California

The Gemological Institute of America (GIA) is a nonprofit institute based in Carlsbad, California. It is dedicated to research and education in the field of gemology and the jewelry arts. Founded in 1931, GIA's mission is to protect buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The institute does so through research, gem identification, diamond grading services, and a variety of educational programs. Through its library and subject experts, GIA acts as a resource of gem and jewelry information for the trade, the public and media outlets.

Synthetic alexandrite is an artificially grown crystalline variety of chrysoberyl, composed of beryllium aluminum oxide (BeAl2O4).

<span class="mw-page-title-main">Tairus</span>

Tairus is a synthetic gemstone manufacturer. It was formed in 1989 as part of Mikhail Gorbachev's perestroika initiative to establish a joint venture between the Russian Academy of Sciences and Tairus Created Gems Co Ltd. of Bangkok, Thailand. Today Tairus is a major supplier of hydrothermally grown gemstones to the jewellery industry. Later, Tairus became a privately held enterprise, operating out of its Bangkok distribution hub under the trade name Tairus, owned by Tairus Created Gems Co Ltd. of Bangkok, Thailand.

<span class="mw-page-title-main">Verneuil method</span> Manufacturing process of synthetic gemstones

The Verneuil method, also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1883 by the French chemist Auguste Verneuil. It is primarily used to produce the ruby, sapphire and padparadscha varieties of corundum, as well as the diamond simulants rutile, strontium titanate and spinel. The principle of the process involves melting a finely powdered substance using an oxyhydrogen flame, and crystallising the melted droplets into a boule. The process is considered to be the founding step of modern industrial crystal growth technology, and remains in wide use to this day.

<span class="mw-page-title-main">Diamond (gemstone)</span> Gemstone

Diamond is a gemstone formed by cutting a raw diamond. Diamonds are one of the best-known and most sought-after gems, and they have been used as decorative items since ancient times.

<span class="mw-page-title-main">Richard W. Hughes</span>

Richard W. Hughes is an American gemologist and author, known as an authority on corundum, rubies and sapphires.

Carroll Chatham (1914–1983) was an American chemist who developed the flux method for synthesizing emeralds. He was the first person to develop a method for creating man-made emeralds that was able to make them commercially available. He founded the jewelry company Chatham which is still selling Chatham emeralds to this day.

References

  1. ↑ "Gemstone". Lexico. Oxford University Press. Archived from the original on March 21, 2020.
  2. ↑ Webster Online Dictionary Archived 2007-06-03 at the Wayback Machine
  3. ↑ Alden, Nancy (2009). Simply Gemstones: Designs for Creating Beaded Gemstone Jewelry. New York, NY: Random House. p. 136. ISBN   978-0-307-45135-4.
  4. ↑ "Pearl | Natural, Cultured & Imitation Gemstones | Britannica". www.britannica.com. January 19, 2024. Retrieved March 1, 2024.
  5. ↑ "Gemopedia - Gemstone Encyclopedia". www.gemstones.com. Retrieved March 1, 2024.
  6. ↑ "Soft Gemstones and Minerals | Gem5.com". gem5.com. Retrieved March 1, 2024.
  7. ↑ "Gemstone Hardness and Wearability".
  8. ↑ "Colored Gemstones Market: Sales Projection Shows 11.6% CAGR Growth Potential by 2033 – Market Research Blog". March 1, 2024. Retrieved March 1, 2024.
  9. ↑ Bauer, Max (1968). Precious Stones. Dover Publications. p. 2. ISBN   9780486219103.
  10. ↑ "What are the differences between precious and semi-precious stones? - Information - Leysen - Joaillier since 1855". www.leysen.eu. Retrieved February 10, 2024.
  11. ↑ Wise, R. W., 2006, Secrets of The Gem Trade, The Connoisseur's Guide to Precious Gemstones, Brunswick House Press, pp. 3–8 ISBN   0-9728223-8-0
  12. ↑ "Crystal Habits and Forms of Minerals and Gems". geology.com. Retrieved March 1, 2024.
  13. ↑ "Diamond". www.thecanadianencyclopedia.ca. Retrieved March 1, 2024.
  14. ↑ Hansen, Robin (April 12, 2022). Gemstones: A Concise Reference Guide. Princeton University Press. p. 47. ISBN   978-0-691-21448-1.
  15. ↑ Read, Peter G. (2005). Gemmology. Butterworth-Heinemann. p. 13. ISBN   978-0-7506-6449-3.
  16. ↑ Hurrell, Karen; Johnson, Mary L. (2017). Gemstones: a complete color reference for precious and semiprecious stones of the world. New York: Chartwell Books. ISBN   978-0-7858-3498-4.
  17. ↑ "Gemstone Identification: How to Identify Gemstones | Gemstones.com". www.gemstones.com. Retrieved March 1, 2024.
  18. ↑ AskOxford.com Concise Oxford English dictionary online.[ full citation needed ]
  19. ↑ Desirable diamonds: The world's most famous gem. by Sarah Todd.[ full citation needed ]
  20. ↑ "Inclusions in Gemstones". www.gia.edu. Retrieved March 1, 2024.
  21. ↑ Wise, R. W., 2006, Secrets of The Gem Trade, The Connoisseur's Guide to Precious Gemstones, Brunswick House Press, p.36 ISBN   0-9728223-8-0
  22. ↑ Wise, R. W., 2006, Secrets of The Gem Trade, The Connoisseur's Guide to Precious Gemstones, Brunswick House Press, p. 15
  23. ↑ "Zoning (Colour Banding)". www.gemporia.com. Retrieved March 1, 2024.
  24. ↑ Church, A.H. (1905). "Definition of Precious Stones". Precious Stones considered in their scientific and artistic relations. His Majesty's Stationery Office, Wyman & Sons. p. 11. Archived from the original on September 29, 2007 – via Farlang.com.
  25. 1 2 3 4 Wise, R. W., 2003, Secrets of The Gem Trade: The Connoisseur's Guide to Precious Gemstones, Brunswick House Press, Lenox, Massachusetts.
  26. ↑ "5 Most Precious Stones". HowStuffWorks.com. November 9, 2009. Archived from the original on November 6, 2014.
  27. ↑ "A complete guide to Gemstones". Jewellery Monthly. April 2, 2015. Archived from the original on August 28, 2017.
  28. ↑ "Pricing of Colored Gemstones | Joseph Menzie Inc". Archived from the original on October 27, 2021. Retrieved October 27, 2021.
  29. ↑ Katz, Michael (2005). Gemstone Energy Medicine: Healing Body, Mind and Spirit. Natural Healing Press. ISBN   9780924700248 . Retrieved April 6, 2020.
  30. ↑ "Geographic Origin Determination of Paraíba Tourmaline". Archived from the original on April 9, 2022. Retrieved March 17, 2022.
  31. ↑ "International Gem Society LLC".
  32. ↑ "The Gem and Jewelry Institute of Thailand (Public Organization)". Bangkok Post.
  33. ↑ "Rapaport report of ICA Gemstone Conference in Dubai". Diamonds.net. May 16, 2007. Archived from the original on July 26, 2011. Retrieved July 30, 2010.
  34. 1 2 3 "A Guide to Gem Cutting Styles".
  35. ↑ Kraus, Pansy D. (2007). Introduction to Lapidary . Krause Publications. ISBN   9780801972669.
  36. ↑ Vargas, Glenn; Vargas, Martha (2002). Faceting For Amateurs. G. & M. Vargas. ISBN   9780917646096.
  37. ↑ "Seeing Color".
  38. ↑ "Ruby and Sapphire: Gems of the Mineral Corundum". geology.com. Retrieved March 1, 2024.
  39. ↑ "Padparadscha Sapphires: 10 Tips On Judging The Rare Gem". The Natural Sapphire Company Blog. April 6, 2015. Archived from the original on January 19, 2018. Retrieved January 19, 2018.
  40. ↑ Nassau, Kurt (1984). Gemstone enhancement: heat, irradiation, impregnation, dyeing, and other treatments which alter the appearance of gemstones, and the detection of such treatments. London u.a: Butterworths. ISBN   978-0-408-01447-2.
  41. 1 2 "An Introduction to Gem Treatments". www.gia.edu. Archived from the original on April 6, 2023. Retrieved March 31, 2023.
  42. 1 2 Nassau, Kurt (1994). Gemstone Enhancement: History, Science and State of the Art (2nd ed.). Oxford: Butterworth Heinemann. ISBN   9780750617970. OCLC   28889342.
  43. ↑ Nassau, Kurt (1984). "The Early History of Gemstone Treatments" (PDF). Archived (PDF) from the original on January 2, 2023. Retrieved March 31, 2023.
  44. ↑ "Tanzanite heating – the science". Archived from the original on 20 June 2016.
  45. ↑ Omi, Nelson M.; Rela, Paulo R. (2007). Gemstone Dedicated Gamma Irradiator Development: Proceedings of the INAC 2007 International Nuclear Atlantic Conference (PDF). Associação Brasileira de Energia Nuclear. p. 1. ISBN   978-85-99141-02-1. Archived from the original (PDF) on October 21, 2022. Retrieved October 21, 2022.
  46. 1 2 Hurlbut, Cornelius S.; Kammerling, Robert C. (1991). Gemology (PDF). Wiley-Interscience. p. 170. ISBN   0-471-52667-3. Archived (PDF) from the original on November 4, 2022. Retrieved November 4, 2022– via LibreTexts.
  47. ↑ Nuclear Regulatory Commission (April 2019). "Backgrounder on Irradiated Gemstones". The U.S. Nuclear Regulatory Commission. Archived from the original on September 1, 2022. Retrieved November 12, 2022.PD-icon.svg This article incorporates public domain material from websites or documents of the United States Government .
  48. ↑ Rossman, George R. (Summer 1981). "Color in Gems: The New Technologies" (PDF). Gems & Gemology . 17 (2). Gemological Institute of America: 70. doi: 10.5741/GEMS.17.2.60 . ISSN   0016-626X. Archived from the original (PDF) on November 12, 2022.
  49. 1 2 Hilson, Gavin (2016). Artisanal and small-scale mining and agriculture: Exploring their links in rural sub-Saharan Africa (Report). International Institute for Environment and Development.
  50. ↑ Fisher, Eleanor (July 2007). "Occupying the Margins: Labour Integration and Social Exclusion in Artisanal Mining in Tanzania". Development and Change. 38 (4): 735–760. doi:10.1111/j.1467-7660.2007.00431.x. ISSN   0012-155X.
  51. ↑ Hinton, Jennifer J; Veiga, Marcello M; Veiga, A.Tadeu C (March 2003). "Clean artisanal gold mining: a utopian approach?". Journal of Cleaner Production. 11 (2): 99–115. Bibcode:2003JCPro..11...99H. doi:10.1016/s0959-6526(02)00031-8. ISSN   0959-6526.
  52. ↑ Hentschel, Thomas (2002). Global Report on Artisanal & Small-Scale Mining. Mining, Minerals and Sustainable Development. ISBN   9978-40-971-8.
  53. ↑ Takam Tiamgne, Xavier; Kalaba, Felix K.; Nyirenda, Vincent R. (September 2022). "Mining and socio-ecological systems: A systematic review of Sub-Saharan Africa". Resources Policy. 78: 102947. Bibcode:2022RePol..7802947T. doi:10.1016/j.resourpol.2022.102947. ISSN   0301-4207.
  54. ↑ Dissanayake, C. B.; Rupasinghe, M. S. (October 1996). "Environmental impact of mining, erosion and sedimentation in Sri Lanka". International Journal of Environmental Studies. 51 (1): 35–50. Bibcode:1996IJEnS..51...35D. doi:10.1080/00207239608711069. ISSN   0020-7233.
  55. ↑ Harrington, Alexandra R. "Faceting the Future: The Need for and Proposal of the Adoption of a Kimberley Process-Styled Legitimacy Certification System for the Global Gemstone Market". Research Gate.
  56. ↑ Jewelers' circular-keystone: JCK. Chilton Company. 1994.[ full citation needed ]
  57. ↑ "New process promises bigger, better diamond crystals". Carnegie Institution for Science. Archived from the original on December 1, 2010. Retrieved January 7, 2011.
  58. 1 2 3 4 5 Weldon, R. "An Introduction to Synthetic Gem Materials" (PDF). Archived (PDF) from the original on April 15, 2023. Retrieved April 14, 2023.
  59. ↑ Shigley, James (2000). "Treated and synthetic gem materials". Current Science. 79 (11): 1566–1571. JSTOR   24104849.
  60. ↑ Elwell, Dennis (1981). Nassau, Kurt (ed.). "Synthetic Gemstones". Science. 211 (4487): 1156. doi:10.1126/science.211.4487.1156.a. ISSN   0036-8075. JSTOR   1685235. PMID   17755153. S2CID   239860410. Archived from the original on April 15, 2023. Retrieved April 15, 2023.
  61. 1 2 Lefever, R (1982). "Synthetic emerald". pubs.geoscienceworld.org. Retrieved March 15, 2023.
  62. ↑ Hervey, P. R.; Foise, J. W. (February 1, 2001). "Synthetic quartz crystal — A review". Mining, Metallurgy & Exploration. 18 (1): 1–4. Bibcode:2001MMExp..18....1H. doi:10.1007/BF03402862. ISSN   2524-3470. S2CID   140031745.
  63. 1 2 3 Scheel, Hans J (April 1, 2000). "Historical aspects of crystal growth technology". Journal of Crystal Growth. 211 (1): 1–12. Bibcode:2000JCrGr.211....1S. doi:10.1016/S0022-0248(99)00780-0. ISSN   0022-0248. Archived from the original on April 15, 2023. Retrieved April 15, 2023.
  64. 1 2 3 4 5 6 Read, Peter G. (1999). Gemmology. Butterworth-Heinemann. ISBN   0-7506-4411-7. OCLC   807757024.
  65. 1 2 Scheel, Hans (2003). Crystal Growth Technology. John Wiley & Sons. ISBN   9780470871683.
  66. 1 2 Arem, Joel. "Understanding Gem Synthetics, Treatments, And Imitations, Part 4: Synthetic Gemstone Guide". International Gem Society. Archived from the original on March 22, 2023. Retrieved March 30, 2023.
  67. ↑ Jayaraman, A (December 28, 2023). "A brief overview of gem materials: Natural and synthetic". Current Science. 79 (11): 1555–1565. JSTOR   24104848. Archived from the original on April 15, 2023.
  68. 1 2 Li, Zhaolin (December 1, 2001). "Study on inclusions in natural and synthetic gems". Chinese Journal of Geochemistry. 20 (4): 324–332. doi:10.1007/BF03166857. ISSN   1993-0364. S2CID   129031255.
  69. ↑ Nassau, Kurt (1990). "Synthetic Gem Materials in the 1980s" (PDF). Gems & Gemology. 26 (1): 50–63. doi:10.5741/GEMS.26.1.50. Archived (PDF) from the original on November 1, 2021. Retrieved April 15, 2023.
  70. ↑ Harris, Daniel C. (September 26, 2003). Tustison, Randal W. (ed.). "A peek into the history of sapphire crystal growth". Window and Dome Technologies VIII. 5078. SPIE: 1–11. Bibcode:2003SPIE.5078....1H. doi:10.1117/12.501428. S2CID   109528895.
  71. ↑ Hansen 2022, p. 206.
  72. 1 2 "10 Gems Rarer and More Valuable Than Diamonds". The Spruce Crafts. Archived from the original on March 31, 2023. Retrieved March 31, 2023.
  73. ↑ Hainschwang, Thomas; Notari, Franck; Massi, Laurent; Armbruster, Thomas; Rondeau, Benjamin; Fritsch, Emmanuel; Nagashima, Mariko (Summer 2010). "Hibonite: A New Gem Mineral" (PDF). Gems & Gemology. 46 (2): 135–138. doi:10.5741/GEMS.46.2.135. Archived (PDF) from the original on December 13, 2017.
  74. ↑ (in French) "Vidéo – Nolwenn Leroy lumineuse et enceinte dans le clip de Gemme". RTL. 19 July 2017.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.