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116-648: The Cabinet des Médailles is a museum containing internationally important collections of coins, engraved gems , and antiquities, with its distant origins in the treasuries of the French kings of the Middle Ages. The disruptions of the Wars of Religion inspired Charles IX (1560–1574) to create the position of a garde particulier des médailles et antiques du roi ("Special guardian of the King's medals and antiques"). Thus

232-442: A cubic crystal system, are often found as octahedrons . Gemstones are classified into different groups , species , and varieties . For example, ruby is the red variety of the species corundum , while any other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow), and morganite (pink), which are all varieties of

348-504: 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

464-423: A double-sided cameo gem with portraits of Holy Roman Emperor Charles V and his wife and son. The Scot James Tassie (1735–1799), and his nephew William (1777–1860) developed methods for taking hard impressions from old gems, and also for casting new designs from carved wax in enamel , enabling a huge production of what are really imitation engraved gems. The fullest catalogue of his impressions ("Tassie gems")

580-407: A drill, which does not allow fine detail. There is no evidence that magnifying lenses were used by gem cutters in antiquity. A medieval guide to gem-carving techniques survives from Theophilus Presbyter . Byzantine cutters used a flat-edged wheel on a drill for intaglio work, while Carolingian ones used round-tipped drills; it is unclear where they learnt this technique from. In intaglio gems at least,

696-487: A favourite topic for antiquaries from the Renaissance onwards, culminating in the work of Philipp von Stosch, described above. Major progress in understanding Greek gems was made in the work of Adolf Furtwängler (1853–1907, father of the conductor, Wilhelm ). Among recent scholars Sir John Boardman (b. 1927) has made a special contribution, again concentrating on Greek gems. Gertrud Seidmann (1919–2013) moved into

812-477: A flattish faced stone that might fit into a ring. Seal engraving covers the inscription that is printed by stamping, which nearly always only contains script rather than images. Other decoration of the seal itself was not intended to be reproduced. The iconography of gems is similar to that of coins, though more varied. Early gems mostly show animals. Gods, satyrs , and mythological scenes were common, and famous statues often represented – much modern knowledge of

928-447: 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

1044-433: A more desirable blue / purple color. A considerable portion of all sapphire and ruby is treated with a variety of heat treatments to improve both color and clarity. When jewelry containing diamonds is heated for repairs, the diamond should be protected with boric acid ; otherwise, the diamond, which is pure carbon, could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies

1160-517: A number of gems owned by St Albans Abbey , including one large Late Roman imperial cameo (now lost) called Kaadmau which was used to induce overdue childbirths – it was slowly lowered, with a prayer to St Alban, on its chain down the woman's cleavage, as it was believed that the infant would flee downwards to escape it, a belief in accordance with the views of the "father of mineralogy", Georgius Agricola (1494–1555) on jasper . Some gems were engraved, mostly with religious scenes in intaglio, during

1276-487: A number of inclusions), cut, unusual optical phenomena within the stone such as color zoning (the uneven distribution of coloring within a gem) and asteria (star effects). Apart from the more generic and commonly used gemstones such as from diamonds , rubies , sapphires , and emeralds , pearls and opal have also been defined as precious in the jewellery trade. Up to the discoveries of bulk amethyst in Brazil in

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1392-580: A related development in Minoan seals , which are often very fine. The Greek tradition emerged in Ancient Greek art under Minoan influence on mainland Helladic culture, and reached an apogee of subtlety and refinement in the Hellenistic period . Pre- Hellenic Ancient Egyptian seals tend to have inscriptions in hieroglyphs rather than images. The biblical Book of Exodus describes the form of

1508-631: A relief image is more impressive than an intaglio one; in the earlier form the recipient of a document saw this in the impressed sealing wax, while in the later reliefs it was the owner of the seal who kept it for himself, probably marking the emergence of gems meant to be collected or worn as jewellery pendants in necklaces and the like, rather than used as seals – later ones are sometimes rather large to use to seal letters. However inscriptions are usually still in reverse ("mirror-writing") so they only read correctly on impressions (or by viewing from behind with transparent stones). This aspect also partly explains

1624-626: 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. Miners , often from disadvantaged backgrounds, endure hazardous working conditions and receive meager wages, contributing to cycles of poverty and exploitation. 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

1740-526: A ring; intaglio designs register most clearly when viewed by the recipient of a letter as an impression in hardened wax. A finely carved seal was practical, as it made forgery more difficult – the distinctive personal signature did not really exist in antiquity. Gems were mostly cut by using abrasive powder from harder stones in conjunction with a hand-drill, probably often set in a lathe . Emery has been mined for abrasive powder on Naxos since antiquity. Some early types of seal were cut by hand, rather than

1856-402: A sad confession for any art-historian." Other Renaissance gems reveal their date by showing mythological scenes derived from literature that were not part of the visual repertoire in classical times, or borrowing compositions from Renaissance paintings, and using "compositions with rather more figures than any ancient engraver would have tolerated or attempted". Among artists, the wealthy Rubens

1972-531: A spy for England in Italy". Among his contemporaries, Stosch made his lasting impression with Gemmæ Antiquæ Cælatæ ( Pierres antiques graveés ) (1724), in which Bernard Picart 's engravings reproduced seventy antique carved hardstones like onyx, jasper and carnelian from European collections. He also encouraged Johann Lorenz Natter (1705–1763) whom Stosch set to copying ancient carved gems in Florence. Frederick

2088-626: A stone is untreated, while another lab might conclude that it is heat-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 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

2204-448: 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

2320-434: 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. Nearly all tanzanite is heated at low temperatures to remove brown undertones and give

2436-509: Is a recognized grading of the gem's luster, transparency, or "brilliance". Very transparent gems are considered " first water ", while "second" or "third water" gems are those of a lesser transparency. Additionally, material or flaws within a stone may be present as inclusions . Gemstones have no universally accepted grading system. Diamonds are graded using a system developed by the Gemological Institute of America (GIA) in

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2552-485: Is a small and usually semi-precious gemstone that has been carved, in the Western tradition normally with images or inscriptions only on one face. The engraving of gemstones was a major luxury art form in the ancient world , and an important one in some later periods. Strictly speaking, engraving means carving in intaglio (with the design cut into the flat background of the stone), but relief carvings (with

2668-522: Is also colored to make the emerald appear of better color as well as clarity. Turquoise is also commonly treated in a similar manner. Fracture filling has been in use with different gemstones such as diamonds, emeralds, and sapphires. In 2006 "glass-filled rubies" received publicity. Rubies over 10 carats (2 g) with large fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly easy to detect. Another treatment method that

2784-440: 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

2900-515: 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. There are a number of laboratories which grade and provide reports on gemstones. Each laboratory has its own methodology to evaluate gemstones. A stone can be called "pink" by one lab while another lab calls it "padparadscha". One lab can conclude

3016-501: 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. 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

3132-563: 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 gemstones are distinct from imitation or simulated gems. Synthetic gems are physically, optically, and chemically identical to

3248-419: 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). The irradiation process is widely practiced in jewelry industry and enabled

3364-819: Is in the Treasury of the Basilica of San Marco in Venice . Many of these retain the medieval mounts which adapted them for liturgical use. Like the Coupe des Ptolémées , most objects in European museums lost these when they became objects of classicist interest from the Renaissance onwards, or when the mounts were removed for the value of the materials, as happened to many in the French Revolution . The collection of 827 engraved gems of Pope Paul II , which included

3480-410: 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

3596-627: Is represented in all or most early cultures from the area, and the Indus Valley civilization . The cylinder seal , whose design appears only when it is rolled over damp clay, from which the flat ring type developed, was the usual form in Mesopotamia , Assyria and other cultures, and spread to the Aegean and Minoan world , including parts of Greece and Cyprus . These were made in various types of stone, not all hardstone, and gold rings were

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3712-467: Is shown, including the eyelashes on one male head, perhaps a portrait. Four gems signed by Dexamenos of Chios are the finest of the period, two showing herons . Relief carving became common in 5th century BC Greece, and gradually most of the spectacular carved gems in the Western tradition were in relief, although the Sassanian and other traditions remained faithful to the intaglio form. Generally

3828-566: The Natural History of Pliny the Elder give a summary art history of the Greek and Roman tradition, and of Roman collecting. According to Pliny Marcus Aemilius Scaurus (praetor 56 BC) was the first Roman collector. As in later periods objects carved in the round from semi-precious stone were regarded as a similar category of object; these are also known as hardstone carvings . One of

3944-815: The French Revolution , a number of precious objects previously kept at the Treasury of Saint-Denis joined the collection of the Cabinet. The Cabinet des Médailles is considered the oldest museum in France. It is located in the former building of the Bibliothèque Nationale, 58 rue Richelieu, Paris I, and can be visited for free every afternoon (13:00–17:00), seven days a week. 48°52′04″N 2°20′18″E  /  48.8678°N 2.3384°E  / 48.8678; 2.3384 Engraved gems An engraved gem , frequently referred to as an intaglio ,

4060-491: The Gonzagas of Mantua (later owned by Lord Arundel), the 2nd Earl of Bessborough , and the brother of Lord Chesterfield , who himself warned his son in one of his Letters against "days lost in poring upon imperceptible intaglios and cameos". The collection, including its single most famous cameo, the " Marlborough gem " depicting an initiation of Cupid and Psyche, was dispersed after a sale in 1899, fortunately timed for

4176-720: The Portland Vase , as a cheaper material for cameos, and one that allowed consistent and predictable layers on even round objects. During the European Middle Ages antique engraved gems were one classical art form which was always highly valued, and a large but unknown number of ancient gems have (unlike most surviving classical works of art) never been buried and then excavated. Gems were used to decorate elaborate pieces of goldsmith work such as votive crowns , book-covers and crosses, sometimes very inappropriately given their subject matter. Matthew Paris illustrated

4292-673: The Royal Collection . The collections of Charles Towneley , Richard Payne Knight and Clayton Mordaunt Cracherode were bought by or bequeathed to the British Museum , founding their very important collection. But the most famous English collection was that formed by the 4th Duke of Marlborough (1739–1817), "which the Duke kept in his bedroom and resorted to as a relief from his ambitious wife, his busy sister and his many children". This included collections formerly owned by

4408-535: The Susanna Crystal , to be viewed through the gem from the unengraved side, so their inscriptions were reversed like the seals. In wills and inventories, engraved gems were often given pride of place at the head of a list of treasures. Some gems in a remarkably effective evocation of classical style were made in Southern Italy for the court of Frederick II, Holy Roman Emperor in the first half of

4524-446: 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. 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

4640-576: The cabinet of curiosities of his uncle Gaston d'Orléans and acquired that of Hippolyte de Béthune, the nephew of Henri IV's minister Sully . In order to keep the collections closer at hand, he removed them from the old royal library in Paris to the Palace of Versailles . When Louis' great-grandson Louis XV had attained majority, the Cabinet was returned to Paris in 1724, to take up its present space in

4756-461: The hoshen , a ceremonial breastplate worn by the high priest, bearing twelve gems engraved with the names of the Twelve tribes of Israel . Round or oval Greek gems (along with similar objects in bone and ivory) are found from the 8th and 7th centuries BC, usually with animals in energetic geometric poses, often with a border marked by dots or a rim. Early examples are mostly in softer stones. Gems of

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4872-515: The menorah . Many gems are inscribed in the Islamic world, typically with verses from the Koran , and sometimes gems in the Western tradition just contain inscriptions. Many Asian and Middle Eastern cultures have their own traditions, although for example the important Chinese tradition of carved gemstones and hardstones, especially jade carving , is broader than the European one of concentration on

4988-592: The "Felix gem" of Diomedes with the Palladium , was acquired by Lorenzo il Magnifico ; the Medici collection included many other gems and was legendary, valued in inventories much higher than his Botticellis . Somewhat like Chinese collectors, Lorenzo had all his gems inscribed with his name. The Gonzaga Cameo passed through a series of famous collections before coming to rest in the Hermitage . First known in

5104-420: The 13th century, several in the Cabinet des Médailles in Paris. Meanwhile, the church led the development of large, often double-sided, metal seal matrices for wax seals that were left permanently attached to charters and similar legal documents, dangling by a cord, though smaller ring seals that were broken when a letter was opened remained in use. It is not clear to what extent this also continued practices in

5220-415: 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

5336-420: The 6th century are more often oval, with a scarab back (in the past this type was called a "scarabaeus"), and human or divine figures as well as animals; the scarab form was apparently adopted from Phoenicia . The forms are sophisticated for the period, despite the usually small size of the gems. In the 5th century gems became somewhat larger, but still only 2-3 centimetres tall. Despite this, very fine detail

5452-528: The British aristocrats he tutored in connoisseurship; his own collection was described in A.F. Gori , Le gemme antiche di Anton Maria Zanetti (Venice, 1750), illustrated with eighty plates of engravings from his own drawings. Baron Philipp von Stosch (1691–1757), a Prussian who lived in Rome and then Florence, was a major collector, as well as a dealer in engraved gems: "busy, unscrupulous, and in his spare time

5568-483: The Great had opened up new trade routes to the Greek world and increased the range of gemstones available. Roman gems generally continued Hellenistic styles, and can be hard to date, until their quality sharply declines at the end of the 2nd century AD. Philosophers are sometimes shown; Cicero refers to people having portraits of their favourite on their cups and rings. The Romans invented cameo glass , best known from

5684-631: The Great of Prussia bought Stosch's collection in 1765 and built the Antique Temple in the park of the Sanssouci Palace to house his collections of ancient sculpture, coins and over 4,000 gems – the two were naturally often grouped together. The gems are now in the Antikensammlung Berlin . The collection of Joseph Smith , British consul in Venice was bought by King George III of Great Britain and remains in

5800-731: The Great 's collection is in the Hermitage Museum ; one large collection she had bought was the gems from the Orléans Collection . Louis XV of France hired Dominique Vivant to assemble a collection for Madame de Pompadour . In the eighteenth century British aristocrats were able to outcompete even the agents for royal and princely collectors on the Continent, aided by connoisseur-dealers like Count Antonio Maria Zanetti and Philipp von Stosch . Zanetti travelled Europe in pursuit of gems hidden in private collections for

5916-687: The Hellenistic repertoire of subjects, though portraits in contemporary styles were also produced. Famous collectors begin with King Mithridates VI of Pontus (d. 63 BC), whose collection was part of the booty of Pompey the Great , who donated it to the Temple of Jupiter in Rome. Julius Caesar was determined to excel Pompey in this as in other areas, and later gave six collections to his own Temple of Venus Genetrix ; according to Suetonius gems were among his varied collecting passions. Many later emperors also collected gems. Chapters 4-6 of Book 37 of

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6032-530: The King of Prussia which now form the Daktyliothek Poniatowski in Berlin , where they were recognised as modern in 1832, mainly because the signatures of ancient artists from very different times were found on gems in too consistent a style. As in other fields, not many ancient artists' names are known from literary sources, although some gems are signed. According to Pliny, Pyrgoteles was

6148-544: The Portland Vase and the Marlborough gem , a famous head of Antinous , and interpreted in jasperware casts from antique gems by James Tassie. John Flaxman 's neoclassical designs for jasperware were carried out in the extremely low relief typical of cameo production. Some other porcelain imitated three-layer cameos purely by paint, even in implausible objects like a flat Sèvres tea-tray of 1840. Gems were

6264-509: The Roman statues and sarcophagi being newly excavated, antique gems were prime sources for artists eager to regain a classical figurative vocabulary. Cast bronze copies of gems were made, which circulated around Italy, and later Europe. Among very many examples of borrowings that can be traced confidently, the Felix or Diomedes gem owned by Lorenzo de' Medici (see below), with an unusual pose,

6380-559: The advice of Francesco Maria Zanetti and Francesco Ficoroni ; 170 of the Carlisle gems, both Classical and post-Classical, were purchased in 1890 for the British Museum . By the mid-eighteenth century prices had reached such a level that major collections could only be formed by the very wealthy; lesser collectors had to make do with collecting plaster casts , which was also very popular, or buying one of many sumptuously illustrated catalogues of collections that were published. Catherine

6496-482: The allies after Napoleon's defeat, and published at his own expense a history of the collection and description, as newly rearranged according to historical principles, in 1838 Earlier printed catalogues of parts of the collection had been published. Pierre-Jean Mariette , urged by the comte de Caylus, published a selection of the royal carved hardstones as volume II of his Traité des pierres gravées . Louis XIV of France , an acquisitive connoisseur, brought together

6612-576: The ancient world. The late medieval French and Burgundian courts collected and commissioned gems, and began to use them for portraits. The British Museum has what is probably a seated portrait of John, Duke of Berry in intaglio on a sapphire , and the Hermitage has a cameo head of Charles VII of France . Interest had also revived in Early Renaissance Italy, where Venice soon became a particular centre of production. Along with

6728-529: The basis of their alleged healing powers. 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. 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

6844-484: The cabinet of the Flemish antiquary Abraham Gorlaeus in 1609, and engraved gems featured among the antiquities assembled by Thomas Howard, 21st Earl of Arundel . Later in the century William Cavendish, 2nd Duke of Devonshire , formed a collection of gems that is still conserved at Chatsworth . In the eighteenth century a more discerning cabinet of gems was assembled by Henry Howard, 4th Earl of Carlisle , acting upon

6960-648: The cameo is Alexandrian work of the 3rd century BC, or a Julio-Claudian imitation of the style from the 1st century AD. Three of the largest cameo gems from antiquity were created for members of the Julio-Claudian dynasty and seem to have survived above ground since antiquity. The large Gemma Augustea appeared in 1246 in the treasury of the Basilique St-Sernin, Toulouse . In 1533, King François I appropriated it and moved it to Paris, where it soon disappeared around 1590. Not long thereafter it

7076-604: The collecting of impressions in plaster or wax from gems, which may be easier to appreciate than the original. The cameo, which is rare in intaglio form, seems to have reached Greece around the 3rd century; the Farnese Tazza is the only major surviving Hellenistic example (depending on the date assigned to the Gonzaga Cameo – see below), but other glass-paste imitations with portraits suggest that gem-type cameos were made in this period. The conquests of Alexander

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7192-469: The collection of Isabella d'Este , it passed to the Gonzaga Dukes of Mantua , Emperor Rudolf II , Queen Christina of Sweden , Cardinal Decio Azzolini , Livio Odescalchi , Duke of Bracciano , and Pope Pius VI before Napoleon carried it off to Paris, where his Empress Joséphine gave it to Alexander I of Russia after Napoleon's downfall, as a token of goodwill. It remains disputed whether

7308-451: The collection, which has been augmented and never again dispersed – unlike the first royal library, assembled at the Palais du Louvre by Charles V , which contained 973 volumes when it was inventoried in 1373, but was dispersed during the following century. It passed from being the personal collection of the king to becoming a national property – a bien national – as the royal collection

7424-455: 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. Emeralds containing natural fissures are sometimes filled with wax or oil to disguise them. This wax or oil

7540-525: The colorless diamond), and very hard with a hardness score of 8 to 10 on the Mohs scale . Other stones are classified by their color, translucency , and hardness. The traditional distinction does not necessarily reflect modern values; for example, while garnets are relatively inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald. Another traditional term for semi-precious gemstones used in art history and archaeology

7656-467: The connoisseur Rascas de Bagarris garde particulier des médailles et antiques du roi , the "particular guardian of the medals and antiquities of the King". Among the antiquarians and scholars who have had the charge of the Cabinet des Médailles , one of the most outstanding was Théophile Marion Dumersan , who began working there in 1795 at the age of sixteen, protected the collection from dispersal by

7772-673: The constant discovery of new source locations. Determining a "country of origin" is thus much more difficult than determining other aspects of a gem (such as cut, clarity, etc.). Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate. A few gemstones are used as gems in the crystal or other 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

7888-444: The creation of gemstone colors that do not exist or are extremely rare in nature. 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. Virtually all blue topaz , both the lighter and the darker blue shades such as "London" blue, has been irradiated to change

8004-436: The design projecting out of the background as in nearly all cameos ) are also covered by the term. This article uses cameo in its strict sense, to denote a carving exploiting layers of differently coloured stone. The activity is also called gem carving and the artists gem-cutters . References to antique gems and intaglios in a jewellery context will almost always mean carved gems; when referring to monumental sculpture ,

8120-520: 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. Other methods recorded 2000 years ago in the book Natural History by Pliny the Elder include oiling and dyeing/staining. 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

8236-410: The early 1950s. Historically, all gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision). A mnemonic device , the "four Cs" (color, cut, clarity, and carats), has been introduced to help describe the factors used to grade

8352-438: The engraved gem. Another offshoot of the mania for engraved gems is the fine-grained slightly translucent stoneware called jasperware that was developed by Josiah Wedgwood and perfected in 1775. Though white-on-blue matte jasperware is the most familiar Wedgwood ceramic line, still in production today and widely imitated since the mid-19th century, white-on-black was also produced. Wedgwood made notable jasperware copies of

8468-410: 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. Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds will always have

8584-445: The eye as the perceived color. 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 ) but exhibit different colors because of impurities which absorb and reflect different wavelengths of light depending on their individual compositions. Even

8700-439: The fact that these impurities can be "manipulated", thus changing the color of the gem. Gemstones are often treated to enhance the color or clarity of the stone. 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. Depending on

8816-451: 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 2 O 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. For example, diamonds, which have

8932-417: The flat facets. Rarely, some cutters use special curved laps to cut and polish curved facets. The color of any material is due to the nature of light itself. Daylight, often called white light, is 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

9048-668: The gemstone trade no longer makes such a distinction. Many gemstones are used in even the most expensive jewelry, depending on the brand-name of the designer, fashion trends, market supply, treatments, etc. Nevertheless, diamonds, rubies, sapphires, and emeralds still have a reputation that exceeds those of other gemstones. Rare or unusual gemstones, generally 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 . Gemstone pricing and value are governed by factors and characteristics in

9164-425: The gemstone's durability to be increased. 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. A situation that arises as

9280-566: The largest, the Coupe des Ptolémées was probably donated to the Basilica of Saint-Denis , near Paris, by Charles the Bald , as the inscription on its former gem-studded gold Carolingian mounting stated; it may have belonged to Charlemagne . One of the best collections of such vessels, though mostly plain without carved decoration, was looted from Constantinople in the Fourth Crusade , and

9396-545: The later Archaic period. Portraits of monarchs are found from the Hellenistic period onwards, although as they do not usually have identifying inscriptions, many fine ones cannot be identified with a subject. In the Roman Imperial period, portraits of the imperial family were often produced for the court circle, and many of these have survived, especially a number of spectacular cameos from the time of Augustus . As private objects, produced no doubt by artists trained in

9512-419: 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

9628-435: 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 . 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

9744-516: The most common on the market currently. Synthetic corundum includes ruby (red variation) and sapphire (other color variations), both of which are considered highly desired and valued. Ruby was the first gemstone to be synthesized by Auguste Verneuil with his development of the flame-fusion process in 1902. 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. The most common synthesized beryl

9860-538: The natural stone, but are created in a laboratory. 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

9976-619: The new American museums and provided the core of the collection of the Metropolitan in New York and elsewhere, with the largest group still together being about 100 in the Walters Art Museum , Baltimore. Prince Stanisław Poniatowski (1754–1833) "commissioned about 2500 gems and encouraged the belief that they were, in fact, ancient." He presented a set of 419 plaster impressions of his collection of Poniatowski gems to

10092-496: The number of gems that were not what they seemed to be scared collectors. Among the last practitioners was James Robertson , who sensibly moved into the new art of photography . Perhaps the best known gem engraver of the 20th century, working in a contemporary idiom, is the British artist Ronald Pennell , whose work is held in the British Crafts Council Collection among many others. Cameo glass

10208-550: The only artist allowed to carve gems for the seal rings of Alexander the Great . Most of the most famous Roman artists were Greeks, like Dioskurides, who is thought to have produced the Gemma Augustea, and is recorded as the artist of the matching signet rings of Augustus – very carefully controlled, they allowed orders to be issued in his name by his most trusted associates. Other works survive signed by him (rather more than are all likely to be genuine), and his son Hyllos

10324-616: The period both in Byzantium and Europe. In the West production revived from the Carolingian period , when rock crystal was the commonest material. The Lothair Crystal (or Suzanna Crystal , British Museum , 11.5 cm diameter), clearly not designed for use as a seal, is the best known of 20 surviving Carolingian large intaglio gems with complex figural scenes, although most were used for seals. Several crystals were designed, like

10440-445: The poses of lost Greek cult statues such as Athena Promachos comes from the study of gems, which often have clearer images than coins. A 6th(?) century BC Greek gem already shows Ajax committing suicide, with his name inscribed. The story of Heracles was, as in other arts, the most common source of narrative subjects. A scene may be intended as the subject of an early Archaic gem, and certainly appears on 6th century examples from

10556-689: 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. 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. Unregulated mining practices often result in deforestation , soil erosion , and water contamination thus threatening ecosystems and biodiversity . Unregulated mining activity can also cause depletion of natural resources, thus diminishing

10672-804: The prevalence of illicit practices undermine market integrity and trust. 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

10788-450: The prospects for sustainable development . 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

10904-507: 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. In the addition to the aesthetic and adorning/ornamental purpose of gemstones, there are many proponents of energy medicine who also value gemstones on

11020-469: The recessed cut surface is usually very well preserved, and microscopic examination is revealing of the technique used. The colour of several gemstones can be enhanced by a number of artificial methods, using heat, sugar and dyes. Many of these can be shown to have been used since antiquity – since the 7th millennium BC in the case of heating. The technique has an ancient tradition in the Near East , and

11136-542: The royal library that was designed under the direction of Jules-Robert de Cotte , the son of Mansart 's successor at the Bâtiments du Roi . In the Cabinet des Médailles , the medal-cabinet delivered in 1739 by the ébéniste du roi Antoine Gaudreau figures among the greatest pieces of French furniture. Other medal cabinets were delivered for Louis XIV by André-Charles Boulle . The cabinet also still houses its paintings by Boucher , Natoire and Van Loo . Following

11252-531: 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. Whether

11368-426: The same named gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called " padparadscha sapphire ". This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition and structure, they are not exactly

11484-417: The same types of sardonyx and other hardstones and using virtually the same techniques, produced classicizing works of glyptic art, often intended as forgeries, in such quantity that they compromised the market for them, as Gisela Richter observed in 1922. Even today, Sir John Boardman admits that "We are sometimes at a loss to know whether what we are looking at belongs to the 1st or the 15th century AD,

11600-492: 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

11716-404: The stone's color, luster and other surface properties as opposed to internal reflection properties like brilliance. Grinding wheels and polishing agents are used to grind, shape, and polish the smooth dome shape of the stones. 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

11832-897: The subject, having previously been a German teacher. Semi-precious 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 . 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. Most gemstones are hard, but some softer minerals such as brazilianite may be used in jewelry 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. Found all over

11948-524: 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. 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. Some gemstones are more difficult to synthesize than others and not all stones are commercially viable to attempt to synthesize. These are

12064-584: The term counter-relief , meaning the same as intaglio , is more likely to be used. Vessels like the Cup of the Ptolemies and heads or figures carved in the round are also known as hardstone carvings . Glyptics or glyptic art covers the field of small carved stones, including cylinder seals and inscriptions, especially in an archaeological context. Though they were keenly collected in antiquity, most carved gems originally functioned as seals , often mounted in

12180-589: The tradition of Hellenistic monarchies, their iconography is less inhibited than the public state art of the period about showing divine attributes as well as sexual matters. The identity and interpretation of figures in the Gemma Augustea remains unclear. A number of gems from the same period contain scenes apparently from the lost epic on the Sack of Troy , of which the finest is by Dioskurides ( Chatsworth House ). Renaissance and later gems remain dominated by

12296-419: 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. 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

12412-410: 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. A gem expert is a gemologist , a gem maker is called a lapidarist or gemcutter ; a diamond cutter is called a diamantaire . The traditional classification in the West, which goes back to

12528-566: Was a notable collector. Engraved gems occur in the Bible , especially when the hoshen and ephod worn by the High Priest are described; though these were inscribed with the names of the tribes of Israel in letters, rather than any images. A few identifiably Jewish gems survive from the classical world, including Persia, mostly with the owner's name in Hebrew, but some with symbols such as

12644-800: Was also a gem engraver. The Anichini family were leading artists in Venice and elsewhere in the 15th and 16th centuries. Many Renaissance artists no doubt kept their activities quiet, as they were passing their products off as antique. Other specialist carvers included Giovanni Bernardi (1494–1553), Giovanni Jacopo Caraglio (c. 1500–1565), Giuseppe Antonio Torricelli (1662–1719), the German-Italian Anton Pichler (1697–1779) and his sons Giovanni and Luigi , Charles Christian Reisen (Anglo-Norwegian, 1680–1725). Other sculptors also carved gems, or had someone in their workshop who did. Leone Leoni said he personally spent two months on

12760-542: Was copied by Leonardo da Vinci and may well have provided the "starting point" for one of Michelangelo 's ignudi on the Sistine Chapel ceiling . Another of Lorenzo's gems supplied, probably via a drawing by Perugino , a pose used by Raphael . By the 16th century carved and engraved gems were keenly collected across Europe for dedicated sections of a cabinet of curiosities , and their production revived, in classical styles; 16th-century gem-cutters working with

12876-561: Was declared during the Revolution . A stage in this aspect of its development was the bequest of the collection of pioneering archeologist comte de Caylus , who knew that in this fashion his antiquities would be most accessible to scholars. Other collectors followed suit: when the duc de Luynes gave his collection of Greek coins to the Cabinet Impérial in 1862, it was a national collection rather than simply an Imperial one he

12992-405: Was enriching. The State also added to the treasury contained in the Cabinet des Médailles: a notable addition, in 1846, was the early sixth century gold Treasure of Gourdon . The cabinet , in the sense of a small private room for the conservation and display of intimate works of art and for private conversations, rather than a piece of furniture, took a stable shape under Henry IV , who nominated

13108-614: Was fenced for 12,000 gold pieces to Emperor Rudolph II; it remains in Vienna , alongside the Gemma Claudia . The largest flat engraved gem known from antiquity is the Great Cameo of France , which entered (or re-entered) the French royal collection in 1791 from the treasury of Sainte-Chapelle , where it had been since at least 1291. In England, a false dawn of gem collecting was represented by Henry, Prince of Wales ' purchase of

13224-561: Was invented by the Romans in about 30BC to imitate engraved hardstone cameos, with the advantage that consistent layering could be achieved even on round vessels – impossible with natural gemstones. It was however very difficult to manufacture and surviving pieces, most famously the Portland Vase , are actually much rarer than Roman gemstone cameos. The technique was revived in the 18th and especially 19th centuries in England and elsewhere, and

13340-507: Was most effectively used in French Art Nouveau glass that made no attempt to follow classical styles. The Middle Ages, which lived by charters and other sealed documents, were at least as keen on using seals as the ancient world, now creating them for towns and church institutions, but they normally used metal matrices and signet rings . However some objects, like a 13th-century Venetian Seven Sleepers of Ephesus , mimicked

13456-579: Was published in 1791, with 15,800 items. There are complete sets of the impressions in the Hermitage, the Victoria & Albert Museum in London, and in Edinburgh. Other types of imitation became fashionable for ladies' brooches , such as ceramic cameos by Josiah Wedgwood in jasperware . The engraved gem fell permanently out of fashion from about the 1860s, perhaps partly as a growing realization of

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