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58-622: The Sunrise Ruby has been the world's most expensive ruby , most expensive coloured gemstone, and most expensive gemstone other than a diamond until the discovery of the Estrela de Fura . Originally mined in Myanmar , its current name is derived from a poem of the same name, written by the 13th-century Sufi poet Rumi . It is a 25.59-carat (5.1 g) Burmese "pigeon blood" ruby, mounted by Cartier and set between heptagonal diamonds weighing 2.47 carats (0.49 g) and 2.70 carats (0.54 g). It

116-448: A Mohs hardness of 10.0 and moissanite falling somewhere in between corundum (ruby) and diamond in hardness. Sapphire, ruby, and pure corundum are α-alumina, the most stable form of Al 2 O 3 , in which 3 electrons leave each aluminium ion to join the regular octahedral group of six nearby O ions; in pure corundum this leaves all of the aluminium ions with a very stable configuration of no unpaired electrons or unfilled energy levels, and

174-484: A decrease in the material's hardness. The way to inhibit the movement of planes of atoms, and thus make them harder, involves the interaction of dislocations with each other and interstitial atoms. When a dislocation intersects with a second dislocation, it can no longer traverse through the crystal lattice. The intersection of dislocations creates an anchor point and does not allow the planes of atoms to continue to slip over one another A dislocation can also be anchored by

232-424: A different type of atom at the lattice site that should normally be occupied by a metal atom, a substitutional defect is formed. If there exists an atom in a site where there should normally not be, an interstitial defect is formed. This is possible because space exists between atoms in a crystal lattice. While point defects are irregularities at a single site in the crystal lattice, line defects are irregularities on

290-401: A lighter red color than gemstone ruby and are referred to as pink ruby ." 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

348-540: A little chromium at red heat . In 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process, later also known as the Verneuil process . By 1910, Verneuil's laboratory had expanded into a 30 furnace production facility, with annual gemstone production having reached 1,000 kilograms (2,000 lb) in 1907. Other processes in which synthetic rubies can be produced are through Czochralski's pulling process , flux process, and

406-413: A plane of atoms. Dislocations are a type of line defect involving the misalignment of these planes. In the case of an edge dislocation, a half plane of atoms is wedged between two planes of atoms. In the case of a screw dislocation two planes of atoms are offset with a helical array running between them. In glasses, hardness seems to depend linearly on the number of topological constraints acting between

464-410: A ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red, called blood-red or pigeon blood, commands a large premium over other rubies of similar quality. After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that

522-464: A tensile test. This relationship can be used to describe how the material will respond to almost any loading situation, often by using the Finite Element Method (FEM). This applies to the outcome of an indentation test (with a given size and shape of indenter, and a given applied load). However, while a hardness number thus depends on the stress-strain relationship, inferring the latter from

580-553: Is lead glass filling. Filling the fractures inside the ruby with lead glass (or a similar material) dramatically improves the transparency of the stone, making previously unsuitable rubies fit for applications in jewelry. The process is done in four steps: If a color needs to be added, the glass powder can be "enhanced" with copper or other metal oxides as well as elements such as sodium, calcium, potassium etc. The second heating process can be repeated three to four times, even applying different mixtures. When jewelry containing rubies

638-600: Is considered among the rarest of all gemstones. The Swiss Gemmological Institute has described it as "a unique treasure of nature" and praised its "well-proportioned cut, highly attractive colour and fine purity". The Gubelin Gem Lab in Lucerne stated that "such a combination of characteristics is very rare in Burmese rubies of this size." The global chairman of Sotheby's International Jewellery Division, David Bennett, when interviewed on

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696-413: Is defined to be red. All other hues of the gem species corundum are called sapphire. Ruby may exhibit a range of secondary hues, including orange, purple, violet, and pink. Because rubies host many inclusions, their clarity is evaluated by the inclusions’ size, number, location, and visibility. Rubies with the highest clarity grades are known as “eye-clean,” because their inclusions are the least visible to

754-710: Is heated (for repairs) it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond. The treatment can be identified by noting bubbles in cavities and fractures using a 10× loupe. In 1837, Gaudin made the first synthetic rubies by fusing potash alum at a high temperature with a little chromium as a pigment. In 1847, Ebelmen made white sapphire by fusing alumina in boric acid. In 1877, Edmond Frémy and industrial glass-maker Charles Feil made crystal corundum from which small stones could be cut. In 1887, Fremy and Auguste Verneuil manufactured artificial ruby by fusing BaF 2 and Al 2 O 3 with

812-665: Is known as a scleroscope . Two scales that measures rebound hardness are the Leeb rebound hardness test and Bennett hardness scale. Ultrasonic Contact Impedance (UCI) method determines hardness by measuring the frequency of an oscillating rod. The rod consists of a metal shaft with vibrating element and a pyramid-shaped diamond mounted on one end. There are five hardening processes: Hall-Petch strengthening , work hardening , solid solution strengthening , precipitation hardening , and martensitic transformation . In solid mechanics , solids generally have three responses to force , depending on

870-459: Is known as the Hall-Petch relationship . However, below a critical grain-size, hardness decreases with decreasing grain size. This is known as the inverse Hall-Petch effect. Hardness of a material to deformation is dependent on its microdurability or small-scale shear modulus in any direction, not to any rigidity or stiffness properties such as its bulk modulus or Young's modulus . Stiffness

928-407: Is often confused for hardness. Some materials are stiffer than diamond (e.g. osmium) but are not harder, and are prone to spalling and flaking in squamose or acicular habits. The key to understanding the mechanism behind hardness is understanding the metallic microstructure , or the structure and arrangement of the atoms at the atomic level. In fact, most important metallic properties critical to

986-557: 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 . Some gemstones that are popularly or historically called rubies, such as the Black Prince's Ruby in the British Imperial State Crown , are actually spinels . These were once known as "Balas rubies". The quality of

1044-413: Is the sclerometer . Another tool used to make these tests is the pocket hardness tester . This tool consists of a scale arm with graduated markings attached to a four-wheeled carriage. A scratch tool with a sharp rim is mounted at a predetermined angle to the testing surface. In order to use it a weight of known mass is added to the scale arm at one of the graduated markings, the tool is then drawn across

1102-453: Is the measure of how resistant a sample is to fracture or permanent plastic deformation due to friction from a sharp object. The principle is that an object made of a harder material will scratch an object made of a softer material. When testing coatings, scratch hardness refers to the force necessary to cut through the film to the substrate. The most common test is Mohs scale , which is used in mineralogy . One tool to make this measurement

1160-399: Is the most important factor. Color divides into three components: hue , saturation and tone . Hue refers to color as we normally use the term. Transparent gemstones occur in the pure spectral hues of red, orange, yellow, green, blue, violet. In nature, there are rarely pure hues, so when speaking of the hue of a gemstone, we speak of primary and secondary and sometimes tertiary hues. Ruby

1218-485: Is the only country in mainland Europe to have naturally occurring rubies. They can mainly be found around the city of Prilep . Macedonian rubies have a unique raspberry color. A few rubies have been found in the U.S. states of Montana , North Carolina , South Carolina and Wyoming . Spinel , another red gemstone, is sometimes found along with rubies in the same gem gravel or marble. Red spinels may be mistaken for rubies by those lacking experience with gems. However,

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1276-436: Is the tendency of a material to fracture with very little or no detectable plastic deformation beforehand. Thus in technical terms, a material can be both brittle and strong. In everyday usage "brittleness" usually refers to the tendency to fracture under a small amount of force, which exhibits both brittleness and a lack of strength (in the technical sense). For perfectly brittle materials, yield strength and ultimate strength are

1334-760: The hydrothermal process . Most synthetic rubies originate from flame fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the naked eye but magnification may reveal curved striae and gas bubbles. The fewer the number and the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections (i.e., a perfect ruby), in which case it will be suspected of being artificial. Dopants are added to some manufactured rubies so they can be identified as synthetic, but most need gemological testing to determine their origin. Synthetic rubies have technological uses as well as gemological ones. Rods of synthetic ruby are used to make ruby lasers and masers . The first working laser

1392-817: The 17th century techniques were developed to color foil red—by burning scarlet wool in the bottom part of the furnace—which was then placed under the imitation stone. Trade terms such as balas ruby for red spinel and rubellite for red tourmaline can mislead unsuspecting buyers. Such terms are therefore discouraged from use by many gemological associations such as the Laboratory Manual Harmonisation Committee (LMHC). Hardness There are three main types of hardness measurements: scratch, indentation, and rebound. Within each of these classes of measurement there are individual measurement scales. For practical reasons conversion tables are used to convert between one scale and another. Scratch hardness

1450-525: The Aappaluttoq mine in Greenland began running. The rubies in Greenland are said to be among the oldest in the world at approximately 3 billion years old. The Aappaluttoq mine in Greenland is located 160 kilometers south of Nuuk, the capital of Greenland. The rubies are traceable from mine to market. The Montepuez ruby mine in northeastern Mozambique is situated on one of the most significant ruby deposits in

1508-892: The International Colored Gemstone Association (ICGA) have adopted the broader definition for ruby which encompasses its lighter shades, including pink. Historically, rubies have been mined in Thailand, in the Pailin and Samlout District of Cambodia , as well as in Afghanistan , Australia , Brazil , Colombia , India , Namibia , Japan , and Scotland. After the Second World War , ruby deposits were found in Madagascar , Mozambique , Nepal, Pakistan, Tajikistan , Tanzania , and Vietnam . The Republic of North Macedonia

1566-496: The United States, a minimum color saturation must be met to be called a ruby; otherwise, the stone will be called a pink sapphire . Drawing a distinction between rubies and pink sapphires is relatively new, having arisen sometime in the 20th century. Often, 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

1624-399: The above wavelengths stimulates fluorescent emission of 694-nanometer-wavelength red light, which adds to its red color and perceived luster . The chromium concentration in artificial rubies can be adjusted (in the crystal growth process) to be ten to twenty times less than in the natural gemstones. Theodore Maiman says that "because of the low chromium level in these crystals they display

1682-451: The amount of force and the type of material: Strength is a measure of the extent of a material's elastic range, or elastic and plastic ranges together. This is quantified as compressive strength , shear strength , tensile strength depending on the direction of the forces involved. Ultimate strength is an engineering measure of the maximum load a part of a specific material and geometry can withstand. Brittleness , in technical usage,

1740-475: The atoms of the network. Hence, the rigidity theory has allowed predicting hardness values with respect to composition. Dislocations provide a mechanism for planes of atoms to slip and thus a method for plastic or permanent deformation. Planes of atoms can flip from one side of the dislocation to the other effectively allowing the dislocation to traverse through the material and the material to deform permanently. The movement allowed by these dislocations causes

1798-458: The critical dimensions of an indentation left by a specifically dimensioned and loaded indenter. Common indentation hardness scales are Rockwell , Vickers , Shore , and Brinell , amongst others. Rebound hardness , also known as dynamic hardness , measures the height of the "bounce" of a diamond-tipped hammer dropped from a fixed height onto a material. This type of hardness is related to elasticity . The device used to take this measurement

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1856-496: The crystal is perfectly colorless, and transparent except for flaws. When a chromium atom replaces an occasional aluminium atom, it too loses 3 electrons to become a chromium ion to maintain the charge balance of the Al 2 O 3 crystal. However, the Cr ions are larger and have electron orbitals in different directions than aluminium. The octahedral arrangement of the O ions is distorted, and

1914-433: The density of dislocations increases, there are more intersections created and consequently more anchor points. Similarly, as more interstitial atoms are added, more pinning points that impede the movements of dislocations are formed. As a result, the more anchor points added, the harder the material will become. Careful note should be taken of the relationship between a hardness number and the stress-strain curve exhibited by

1972-419: The energy levels of the different orbitals of those Cr ions are slightly altered because of the directions to the O ions. Those energy differences correspond to absorption in the ultraviolet, violet, and yellow-green regions of the spectrum. If one percent of the aluminium ions are replaced by chromium in ruby, the yellow-green absorption results in a red color for the gem. Additionally, absorption at any of

2030-509: The evening, bidding lasted approximately seven minutes with buyers via phone as the main source of bidding. The Sunrise Ruby greatly surpassed the previous record holder, the Graff ruby ring, which sold for US$ 8.6 million in November 2014. Its record-setting price has been attributed to the rapid increase in prices for coloured gemstones and public auctions, with figures often "rivaling the performance of

2088-473: The finest red spinels, now heavily sought, can have values approaching all but the finest examples of ruby. The Mogok Valley in Upper Myanmar (Burma) 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 rapidly became

2146-478: The former is far from simple and is not attempted in any rigorous way during conventional hardness testing. (In fact, the Indentation Plastometry technique, which involves iterative FEM modelling of an indentation test, does allow a stress-strain curve to be obtained via indentation, but this is outside the scope of conventional hardness testing.) A hardness number is just a semi-quantitative indicator of

2204-400: The grain level of the microstructure that are responsible for the hardness of the material. These irregularities are point defects and line defects. A point defect is an irregularity located at a single lattice site inside of the overall three-dimensional lattice of the grain. There are three main point defects. If there is an atom missing from the array, a vacancy defect is formed. If there is

2262-471: The intensity of that red light. By arranging mirrors or other means to pass emitted light repeatedly through the crystal, a ruby laser in this way produces a very 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. Usually,

2320-443: The interaction with interstitial atoms. If a dislocation comes in contact with two or more interstitial atoms, the slip of the planes will again be disrupted. The interstitial atoms create anchor points, or pinning points, in the same manner as intersecting dislocations. By varying the presence of interstitial atoms and the density of dislocations, a particular metal's hardness can be controlled. Although seemingly counter-intuitive, as

2378-408: The late 1990s, a large supply of low-cost materials caused a sudden surge in supply of heat-treated rubies, leading to a downward pressure on ruby prices. Improvements used include color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them. The most common treatment is the application of heat. Most rubies at the lower end of

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2436-529: The manufacturing of today’s goods are determined by the microstructure of a material. At the atomic level, the atoms in a metal are arranged in an orderly three-dimensional array called a crystal lattice . In reality, however, a given specimen of a metal likely never contains a consistent single crystal lattice. A given sample of metal will contain many grains, with each grain having a fairly consistent array pattern. At an even smaller scale, each grain contains irregularities. There are two types of irregularities at

2494-472: The market are heat treated to improve color, remove purple tinge , blue patches, and silk. These heat treatments typically occur around temperatures of 1800 °C (3300 °F). Some rubies undergo a process of low tube heat, when the stone is heated over charcoal of a temperature of about 1300 °C (2400 °F) for 20 to 30 minutes. The silk is partially broken, and the color is improved. Another treatment, which has become more frequent in recent years,

2552-412: The material. The latter, which is conventionally obtained via tensile testing , captures the full plasticity response of the material (which is in most cases a metal). It is in fact a dependence of the (true) von Mises plastic strain on the (true) von Mises stress , but this is readily obtained from a nominal stress – nominal strain curve (in the pre- necking regime), which is the immediate outcome of

2610-486: The much-sought-after colored diamonds". Following the death of Horten, the jewel was auctioned by Christie's in Geneva on 10 May 2023 for $ 14.7 million. Ruby Ruby is a pinkish red to blood-red colored gemstone , a variety of the mineral corundum ( aluminium oxide ). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires . Ruby

2668-445: The naked human eye. Rubies may also have thin, intersecting inclusions called silk. Silk can scatter light, brightening the gem's appearance, and the presence of silk can also show whether a ruby has been previously heat treated, since intense heat will degrade a ruby's silk. Improving the quality of gemstones by treating them is common practice. Some treatments are used in almost all cases and are therefore considered acceptable. During

2726-406: The resistance to plastic deformation. Although hardness is defined in a similar way for most types of test – usually as the load divided by the contact area – the numbers obtained for a particular material are different for different types of test, and even for the same test with different applied loads. Attempts are sometimes made to identify simple analytical expressions that allow features of

2784-415: The rough stone is heated before cutting. These days, almost 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

2842-399: The ruby, stated "during his 40 years in the industry, he has never before seen a ruby of this calibre". In a Gubelin grading report, it notes, "ruby is of Burmese origin" and that "its vivid but saturated color, poetically referred to as pigeon blood red, is due to a combination of well balanced trace elements in the stone, typical and characteristic for the finest rubies of Mogok." Gemstones of

2900-453: The same quality typically form in only small crystals, making this one an "extremely rare" gem. The ruby sold for a record US$ 30.42 million on 12 May 2015 at a Sotheby's auction in Geneva , Switzerland, to Heidi Horten . It was originally estimated to be worth between US$ 12 and 18 million prior to auction and bidding started at 11 million Swiss francs or US$ 11.8 million. Also known as lot 502 of

2958-484: The same, because they do not experience detectable plastic deformation. The opposite of brittleness is ductility . The toughness of a material is the maximum amount of energy it can absorb before fracturing, which is different from the amount of force that can be applied. Toughness tends to be small for brittle materials, because elastic and plastic deformations allow materials to absorb large amounts of energy. Hardness increases with decreasing particle size . This

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3016-491: The stone as the light moves or the stone is rotated. Such effects occur when light is reflected off the "silk" (the structurally oriented rutile needle inclusions) in a certain way. This is one example where inclusions increase the value of a gemstone. Furthermore, rubies can show color changes—though this occurs very rarely—as well as chatoyancy or the "cat's eye" effect. Generally, gemstone-quality corundum in all shades of red, including pink, are called rubies. However, in

3074-561: The stone has been treated. Ruby is the traditional birthstone for July and is usually pinker than garnet , although some rhodolite garnets have a similar pinkish hue to most rubies. The world's most valuable ruby to be sold at auction is the Sunrise Ruby , which sold for US$ 34.8 million. 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

3132-464: The stress-strain curve, particularly the yield stress and Ultimate Tensile Stress (UTS), to be obtained from a particular type of hardness number. However, these are all based on empirical correlations, often specific to particular types of alloy: even with such a limitation, the values obtained are often quite unreliable. The underlying problem is that metals with a range of combinations of yield stress and work hardening characteristics can exhibit

3190-412: The test surface. The use of the weight and markings allows a known pressure to be applied without the need for complicated machinery. Indentation hardness measures the resistance of a sample to material deformation due to a constant compression load from a sharp object. Tests for indentation hardness are primarily used in engineering and metallurgy . The tests work on the basic premise of measuring

3248-511: The world's main ruby mining area. The most recently found ruby deposit in Myanmar is in Namya (Namyazeik) located in the northern state of Kachin . In Pakistani Kashmir there are vast proven reserves of millions of rubies, worth up to half a billion dollars. However, as of 2017 there was only one mine (at Chitta Katha) due to lack of investment. In Afghanistan , rubies are mined at Jegdalek. In 2017

3306-429: The world, although, rubies were only discovered here for the first time in 2009. In less than a decade, Mozambique has become the world's most productive source for gem-quality ruby. Rubies, as with other gemstones, are graded using criteria known as the four Cs, namely color, cut, clarity and carat weight. Rubies are also evaluated on the basis of their geographic origin. In the evaluation of colored gemstones, color

3364-563: Was made by Theodore H. Maiman in 1960. Maiman used a solid-state light-pumped synthetic ruby to produce red laser light at a wavelength of 694 nanometers (nm). Ruby lasers are still in use. Rubies are also used in applications where high hardness is required such as at wear-exposed locations in mechanical clockworks, or as scanning probe tips in a coordinate measuring machine . Imitation rubies are also marketed. Red spinels , red garnets , and colored glass have been falsely claimed to be rubies. Imitations go back to Roman times and already in

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