Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, magnesium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gemstone comes in a wide variety of colors. According to the Madras Tamil Lexicon the name comes from the Sinhalese word "thoramalli" or "tōra- molli", applied to a group of gemstones found in Sri Lanka. According to the same source, the Tamil "tuvara-malli" and "toramalli" are derived from the Sinhalese root word; this etymology is given in other standard dictionaries including the Oxford English Dictionary. Brightly colored Sri Lankan gem tourmalines were brought to Europe in great quantities by the Dutch East India Company to satisfy a demand for curiosities and gems. At the time, it was not realised that schorl and tourmaline were the same mineral, as it was only about 1703 that it was discovered that some colored gems were not zircons. Tourmaline was sometimes called the "Ceylonese Magnet" because it could attract and repel hot ashes due to its pyroelectric properties.
Tourmalines were used by chemists in the 19th century to polarize light by shining rays onto a cut and polished surface of the gem. Encountered species and varieties: Schorl species: Brownish black to black—schorl,Dravite species: from the Drave district of Carinthia Dark yellow to brownish black—dravite,Elbaite species: named after the island of Elba, Italy Red or pinkish-red—rubellite variety, Light blue to bluish green—Brazilian indicolite variety, Green—verdelite or Brazilian emerald variety, Colorless—achroite variety; the most common species of tourmaline is the sodium iron endmember of the group. It may account for 95% or more of all tourmaline in nature; the early history of the mineral schorl shows that the name "schorl" was in use prior to 1400 because a village known today as Zschorlau was named "Schorl", the village had a nearby tin mine where, in addition to cassiterite, black tourmaline was found. The first description of schorl with the name "schürl" and its occurrence was written by Johannes Mathesius in 1562 under the title "Sarepta oder Bergpostill".
Up to about 1600, additional names used in the German language were "Schurel", "Schörle", "Schurl". Beginning in the 18th century, the name Schörl was used in the German-speaking area. In English, the names shorl and shirl were used in the 18th century. In the 19th century the names common schorl, schörl, schorl and iron tourmaline were the English words used for this mineral. Dravite called brown tourmaline, is the sodium magnesium rich tourmaline endmember. Uvite, in comparison, is a calcium magnesium tourmaline. Dravite forms multiple series, including schorl and elbaite; the name dravite was used for the first time by Gustav Tschermak, Professor of Mineralogy and Petrography at the University of Vienna, in his book Lehrbuch der Mineralogie for magnesium-rich tourmaline from village Dobrova near Unterdrauburg in the Drava river area, Austro-Hungarian Empire. Today this tourmaline locality at Dobrova, is a part of the Republic of Slovenia. Tschermak gave this tourmaline the name dravite, for the Drava river area, the district along the Drava River in Austria and Slovenia.
The chemical composition, given by Tschermak in 1884 for this dravite corresponds to the formula NaMg36B3Si6O27, in good agreement with the endmember formula of dravite as known today. Dravite varieties include the vanadium dravite. A lithium-tourmaline elbaite was one of three pegmatitic minerals from Utö, Sweden, in which the new alkali element lithium was determined in 1818 by Johan August Arfwedson for the first time. Elba Island, was one of the first localities where colored and colorless Li-tourmalines were extensively chemically analysed. In 1850 Karl Friedrich August Rammelsberg described fluorine in tourmaline for the first time. In 1870 he proved. In 1889 Scharitzer proposed the substitution of by F in red Li-tourmaline from Sušice, Czech Republic. In 1914 Vladimir Vernadsky proposed the name Elbait for lithium-, sodium-, aluminum-rich tourmaline from Elba Island, with the simplified formula HAl6B2Si4O21. Most the type material for elbaite was found at Fonte del Prete, San Piero in Campo, Campo nell'Elba, Elba Island, Province of Livorno, Italy.
In 1933 Winchell published an updated formula for elbaite, H8Na2Li3Al3B6Al12Si12O62, used to date written as NaAl633. The first crystal structure determination of a Li-rich tourmaline was published in 1972 by Donnay and Barton, performed on a pink elbaite from San Diego County, United States; the tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. Its composition varies because of isomorphous replacement, its general formula can be written as XY3Z63V3W,where: X = Ca, Na, K, ▢ = vacancy Y = Li, Mg, Fe2+, Mn2+, Zn, Al, Cr3+, V3+, Fe3+, Ti4+, vacancy Z = Mg, Al, Fe3+, Cr3+, V3+ T = Si, Al, B B = B, vacancy V = OH, O W = OH, F, OA revised nomenclature for the tourmaline group was published in 2011. Tourmaline is a six-member ring cyclosilicate having a trigonal crystal system, it occurs
Jewellery design is the art or profession of designing and creating jewellery. This is one of civilization's earliest forms of decoration, dating back at least seven thousand years to the oldest known human societies in Mesopotamia and Egypt; the art has taken many forms throughout the centuries, from the simple beadwork of ancient times to the sophisticated metalworking and gem cutting known in the modern day. Before an article of jewellery is created, design concepts are rendered followed by detailed technical drawings generated by a jewellery designer, a professional, trained in the architectural and functional knowledge of materials, fabrication techniques, composition and market trends. Traditional hand-drawing and drafting methods are still utilized in designing jewellery at the conceptual stage. However, a shift is taking place to computer-aided design programs like Rhinoceros Matrix. Whereas the traditionally hand-illustrated jewel is translated into wax or metal directly by a skilled craftsman, a CAD model is used as the basis for a CNC cut or 3D printed'wax' pattern to be used in the rubber molding or lost wax casting processes.
Once conceptual/ideation is complete, the design is rendered and fabricated using the necessary materials for proper adaptation to the function of the object. For example, 24K gold was used in ancient jewellery design because it was more accessible than silver as source material. Before the 1st century many civilizations incorporated beads into jewellery. Once the discovery of gemstones and gem cutting became more available, the art of jewellery ornamentation and design shifted; the earliest documented gemstone cut was done by Theophilus Presbyter, who practiced and developed many applied arts and was a known goldsmith. During the 14th century, medieval lapidary technology evolved to include cabochons and cameos. Early jewellery design commissions were constituted by nobility or the church to honor an event or as wearable ornamentation. Within the structure of early methods and repoussé became standard methods for creating ornamental wares to demonstrate wealth, position, or power; these early techniques created a specific complex design element that would forge the Baroque movement in jewellery design.
Jewellery design has remained constant over the years. The fundamental references, production techniques, materials from ages ago are still being used to this day, yet the recent rapid developments in technology and machinery have allowed artists easier alternatives to some of the old methods. These advancements have transformed the significance and social weight jewellery holds; the twentieth century is where this rudimentary change in the public's attitude towards jewellery design and function is most apparent. Traditionally jewels were seen as precious. Additionally, no one trend can be seen as the history of jewellery design for this time period. Throughout the twentieth century jewellery design underwent drastic and continual style changes: Art Nouveau, Art Deco, International Style & organicism, New Look & Pop, Globalization and Minimalism. Jewellery design trends are affected by the economic and social states of the time; the boundaries of styles and trends tend to blur together and the clear stylistic divisions of the past are harder to see during the twentieth century
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 having the same material properties as natural diamonds. Enhanced diamonds are excluded from this definition. A diamond simulant may be 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 by visual inspection; the most common diamond simulants are high-leaded glass and cubic zirconia, both artificial materials. A number of other artificial materials, such as strontium titanate and synthetic rutile have been developed since the mid-1950s, but these are no longer in common use.
Introduced at the end of the 20th century, the lab-grown product moissanite has gained popularity as an alternative to diamond. The high price of gem-grade diamonds, as well as significant ethical concerns of the diamond trade, have created a large demand for diamond simulants. In order to be considered for use as a diamond simulant, a material must possess certain diamond-like properties; the most advanced artificial simulants have properties which approach diamond, but all simulants have one or more features that and differentiate them from diamond. To a gemologist, the most important of differential properties are those that foster non-destructive testing. Non-destructive testing is preferred because most suspected diamonds are cut into gemstones and set in jewelry, if a destructive test fails, it may damage the simulant—an unacceptable outcome for most jewelry owners, as if a stone is not a diamond, it may still be of value. Following are some of the properties by which diamond and its simulants can be compared and contrasted.
The Mohs scale of mineral hardness is a non-linear scale of common minerals' resistances to scratching. Diamond is at the top of this scale, as it is one of the hardest occurring materials known. Since a diamond is unlikely to encounter substances that can scratch it, other than another diamond, diamond gemstones are free of scratches. Diamond's hardness is visually evident by its lustrous facets which are flat, by its crisp, sharp facet edges. For a diamond simulant to be effective, it must be hard relative to most gems. Most simulants fall far short of diamond's hardness, so they can be separated from diamond by their external flaws and poor polish. In the recent past, the so-called "window pane test" was thought to be an assured method of identifying diamond, it is a destructive test wherein a suspect diamond gemstone is scraped against a pane of glass, with a positive result being a scratch on the glass and none on the gemstone. The use of hardness points and scratch plates made of corundum are used in place of glass.
Hardness tests are inadvisable for three reasons: glass is soft and can be scratched by a large number of materials. The specific gravity or density of a gem diamond is constant at 3.52. Most simulants are far above or below this value, which can make them easy to identify if unset. High-density liquids such as diiodomethane can be used for this purpose, but these liquids are all toxic and therefore are avoided. A more practical method is to compare the expected size and weight of a suspect diamond to its measured parameters: for example, a cubic zirconia will be 1.7 times the expected weight of an equivalently sized diamond. Diamonds are cut into brilliants to bring out their brilliance and fire. Both properties are affected by the cut of the stone, but they are a function of diamond's high refractive index of 2.417 and high dispersion of 0.044, as measured by the sodium B and G line interval. Thus, if a diamond simulant's RI and dispersion are too low, it will appear comparatively dull or "lifeless".
Few simulants have approximating RI and dispersion, the close simulants can be separated by an experienced observer. Direct measurements of RI and dispersion are impractical, but several companies have devised reflectivity meters to gauge a material's RI indirectly by measuring how well it reflects an infrared beam; as important is optic character. Diamond and other cubic materials are isotropic, meaning that light entering a stone behaves the same way regardless
A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, together with amethyst, sapphire and diamond; the word ruby comes from Latin for red. The color of a ruby is due to the element chromium; some gemstones that are popularly or called rubies, such as the Black Prince's Ruby in the British Imperial State Crown, are spinels. These were once known as "Balas rubies"; the quality of a ruby is determined by its color and clarity, 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 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. Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems only moissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and moissanite falling somewhere in between corundum and diamond in hardness. Sapphire and pure corundum are α-alumina, the most stable form of Al2O3, in which 3 electrons leave each aluminum ion to join the regular octahedral group of six nearby O2− ions; when a chromium atom replaces an occasional aluminum atom, it too loses 3 electrons to become a chromium3+ ion to maintain the charge balance of the Al2O3 crystal. However, the Cr3 + ions have electron orbitals in different directions than aluminum; the octahedral arrangement of the O2− ions is distorted, the energy levels of the different orbitals of those Cr3+ ions are altered because of the directions to the O2− ions. Those energy differences correspond to absorption in the ultraviolet and yellow-green regions of the spectrum.
If one percent of the aluminum ions are replaced by chromium in ruby, the yellow-green absorption results in a red color for the gem. Additionally, absorption at any of the above wavelengths stimulates fluorescent emission of 694-nanometer-wavelength red light, which adds to its red color and perceived luster. After absorbing short-wavelength light, there is a short interval of time when the crystal lattice of ruby is in an excited state before fluorescence occurs. If 694-nanometer photons pass through the crystal during that time, they can stimulate more fluorescent photons to be emitted in-phase with them, thus strengthening the intensity of that red light. By arranging mirrors or other means to pass emitted light through the crystal, a ruby laser in this way produces a high intensity of coherent red light. All natural rubies have imperfections in them, including color impurities and inclusions of rutile needles known as "silk". Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes.
The rough stone is heated before cutting. These days all rubies are treated in some form, with heat treatment being the most common practice. Untreated rubies of high quality command a large premium; some rubies show a three-point or six-point asterism or "star". These rubies are cut into cabochons to display the effect properly. Asterisms are best visible with a single-light source and move across the stone as the light moves or the stone is rotated; such effects occur. This is one example. Furthermore, rubies can show color changes—though this occurs rarely—as well as chatoyancy or the "cat's eye" effect. Gemstone-quality corundum in all shades of red, including pink, are called rubies. However, in the United States, a minimum color saturation must be met to be called a ruby. Drawing a distinction between rubies and pink sapphires is new, having arisen sometime in the 20th century; the distinction between ruby and pink sapphire is not clear and can be debated. As a result of the difficulty and subjectiveness of such distinctions, trade organizations such as the International Colored Gemstone Association have adopted the broader definition for ruby which encompasses its lighter shades, including pink.
The Mogok Valley in Upper Myanmar was for centuries the world's main source for rubies. That region has produced some exceptional rubies, however in recent years few good rubies have been found. In central Myanmar, the area of Mong Hsu began producing rubies during the 1990s and became the world's main ruby mining area; the most found ruby deposit in Myanmar is in Namya located in the northern state of Kachin. Rubies have been mined in Thailand, in the Pailin and Samlout District of Cambodia, as well as in Afghanistan, Brazil, India, Namibia and Scotland. In Sri Lanka, lighter shades of rubies are more found; the Republic of Macedonia is the only country in mainland Europe to have occurring rubies. They can be found around the city of
Gems & Gemology
Gems & Gemology is a quarterly scientific journal published by the Gemological Institute of America. Each issue is devoted to research on diamonds and pearls. Topics include geographic sources and synthetics, identification techniques. Established in January 1934, Gems & Gemology is geared toward jewelry gemologists. Issues contain updates from the GIA Laboratory and international gemology news. Gems & Gemology is indexed by the Science Citation Index. According to the Journal Citation Reports, its 2016 impact factor is 0.793, ranking it 24th out of 29 journals in the category "Mineralogy". Official website
Emerald is a gemstone and a variety of the mineral beryl colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are included, so their toughness is classified as poor. Emerald is a cyclosilicate; the word "emerald" is derived, from Vulgar Latin: esmaralda/esmaraldus, a variant of Latin smaragdus, which originated in Ancient Greek: σμάραγδος. Emeralds, like all colored gemstones, are graded using four basic parameters–the four Cs of connoisseurship: color, clarity and carat weight. In the grading of colored gemstones, color is by far the most important criterion. However, in the grading of emeralds, clarity is considered a close second. A fine emerald must possess not only a pure verdant green hue as described below, but a high degree of transparency to be considered a top gem. In the 1960s, the American jewelry industry changed the definition of emerald to include the green vanadium-bearing beryl; as a result, vanadium emeralds purchased as emeralds in the United States are not recognized as such in the UK and Europe.
In America, the distinction between traditional emeralds and the new vanadium kind is reflected in the use of terms such as "Colombian emerald". In gemology, color is divided into three components: hue and tone. Emeralds occur in hues ranging from yellow-green to blue-green, with the primary hue being green. Yellow and blue are the normal secondary hues found in emeralds. Only gems that are medium to dark in tone are considered emeralds; the finest emeralds are 75% tone on a scale where 0% tone is colorless and 100% is opaque black. In addition, a fine emerald will be saturated and have a hue, bright. Gray is the normal saturation mask found in emeralds. Emeralds tend to surface breaking fissures. Unlike diamonds, where the loupe standard, i.e. 10× magnification, is used to grade clarity, emeralds are graded by eye. Thus, if an emerald has no visible inclusions to the eye it is considered flawless. Stones that lack surface breaking fissures are rare and therefore all emeralds are treated to enhance the apparent clarity.
The inclusions and fissures within an emerald are sometime described as jardin, because of their mossy appearance. Imperfections can be used to identify a particular stone. Eye-clean stones of a vivid primary green hue, with no more than 15% of any secondary hue or combination of a medium-dark tone, command the highest prices; the relative non-uniformity motivates the cutting of emeralds in cabochon form, rather than faceted shapes. Faceted emeralds are most given an oval cut, or the signature emerald cut, a rectangular cut with facets around the top edge. Most emeralds are oiled as part of the post-lapidary process, in order to fill in surface-reaching cracks so that clarity and stability are improved. Cedar oil, having a similar refractive index, is used in this adopted practice. Other liquids, including synthetic oils and polymers with refractive indexes close to that of emeralds, such as Opticon, are used; these treatments are applied in a vacuum chamber under mild heat, to open the pores of the stone and allow the fracture-filling agent to be absorbed more effectively.
The U. S. Federal Trade Commission requires the disclosure of this treatment when an oil treated emerald is sold; the use of oil is traditional and accepted by the gem trade, although oil treated emeralds are worth much less than un-treated emeralds of similar quality. Other treatments, for example the use of green-tinted oil, are not acceptable in the trade. Gems are graded on a four-step scale; these categories reflect levels of enhancement, not clarity. A gem graded. Laboratories apply these criteria differently; some gemologists consider the mere presence of oil or polymers to constitute enhancement. Others may ignore traces of oil if the presence of the material does not improve the look of the gemstone. Emeralds in antiquity were mined in Egypt at locations on Mount Smaragdus since 1500 BCE, India, Austria since at least the 14th century CE; the Egyptian mines were exploited on an industrial scale by the Roman and Byzantine Empires, by Islamic conquerors. Mining ceased with the discovery of the Colombian deposits.
Colombia is by far the world's largest producer of emeralds, constituting 50–95% of the world production, with the number depending on the year and grade. Emerald production in Colombia has increased drastically in the last decade, increasing by 78% from 2000 to 2010; the three main emerald mining areas in Colombia are Muzo and Chivor. Rare "trapiche" emeralds are found in Colombia, distinguished by ray-like spokes of dark impurities. Zambia is the world's second biggest producer, with its Kafubu River area deposits about 45 km southwest of Kitwe responsible for 20% of the world's production of gem-quality stones in 2004. In the first half of 2011, the Kagem Mines produced 3.74 tons of emeralds. Emeralds are found all over the world in countries such as Afghanistan, Austria, Bulgaria, Canada, Egypt, France, India, Kazakhstan, Mozambique, Nigeria, Pakistan
Computer-aided technologies is the use of computer technology to aid in the design and manufacture of products. Advanced CAx tools merge many different aspects of the product lifecycle management, including design, finite element analysis, production planning, product Computer-aided design Computer-aided architectural design Computer-aided engineering Computer-aided fixture design Computer-aided innovation Computer-aided industrial design Computer-aided manufacturing Computer-aided process planning Computer-aided requirements capture Computer-aided rule definition Computer-aided rule execution Computer-aided software engineering Computer-aided automation Computer-assisted surgery Computer-aided surgical simulation Computational fluid dynamics Component information system Computer-integrated manufacturing Computer Numerical Controlled Electronic design automation Enterprise resource planning Finite element analysis Knowledge-based engineering Manufacturing process management Manufacturing process planning Material requirements planning Manufacturing resource planning Product data management Product lifecycle management Virtual prototyping List of CAx companies LearnCAx Online Education in CAx Technologies