A gemstone is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments. However, certain rocks and occasionally organic materials that are not minerals are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity and notoriety are other characteristics that lend value to gemstones.
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.
Diamond cutting is the practice of shaping a diamond from a rough stone into a faceted gem. Cutting diamonds requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty.
Facets are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure. Gemstones commonly have facets cut into them in order to improve their appearance by allowing them to reflect light.
A diamond cut is a style or design guide used when shaping a diamond for polishing such as the brilliant cut. Cut refers to shape, and also the symmetry, proportioning and polish of a diamond. The cut of a diamond greatly affects a diamond's brilliance—a poorly-cut diamond is less luminous.
Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.
A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds, which are actual diamonds exhibiting the same material properties as natural diamonds. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection.
The Gemological Institute of America (GIA) is a nonprofit institute based in Carlsbad, California. It is dedicated to research and education in the field of gemology and the jewelry arts. Founded in 1931, GIA's mission is to protect buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The institute does so through research, gem identification and diamond grading services and a variety of educational programs. Through its library and subject experts, GIA acts as a resource of gem and jewelry information for the trade, the public and media outlets.
Marcel Tolkowsky, an engineer by education, was a Belgian member of a Jewish family of diamond cutters from Poland. He is generally acknowledged as the father of the modern round brilliant diamond cut. Many of his family have gone on to become noted diamond cutters, including his cousin Lazare Kaplan and his great-nephew Gabi Tolkowsky.
Diamonds were largely inaccessible to investors until the recent advent of regulated commodities, due to a lack of price discovery and transparency. The characteristics of individual diamonds, especially the carat weight, color and clarity, have significant impact on values, but transactions were always private. With the standardized commodity as an underlying asset, several market traded financial instruments have been announced.
The Tiffany Yellow Diamond is one of the largest yellow diamonds ever discovered. Its carat weight was originally 287.42 carats in the rough when discovered in 1878 in the Kimberley mine in South Africa. It was cut into a cushion shape of 128.54 carats with 82 facets—24 more than a traditional round brilliant—to maximize its brilliance. The facet pattern features eight needle-like facets pointing outward from the culet (bottom) facet. Jewelry and diamond historian Herbert Tillander refers to this as a "stellar brilliant cut", and lists the gem in his book, Diamond Cuts in Historic Jewelry – 1381 to 1910 (1995), among other such diamonds: the Cullinan Diamond, the Koh-i-Noor, the Polar Star, the Wittelsbach, and others.
Gabriel S. Tolkowsky was a Belgian diamond cutter. He was known for cutting the famous Centenary Diamond, and was one of the world's most renowned diamond cutters. The great nephew of Marcel Tolkowsky, father of the modern round brilliant diamond cut, he is the sixth generation in his family to become well-known in the diamond cutting trade.
Diamond is one of the best-known and most sought-after gemstones. They have been used as decorative items since ancient times.
International Gemological Institute (IGI) is a Belgian diamond, colored stone and jewelry certification organization. Established in 1975, it is the largest independent gemological laboratory worldwide.
Richard T. Liddicoat, Jr. was an American gemologist. Liddicoat was an educator in gemology, who made contributions in the area of diamond quality grading and gem identification. Liddicoat was the Chairman of the Board of Governors at the Gemological Institute of America (GIA).
ImaGem Inc. is a gem information company based on patented technology for grading and identifying gems. The parent company, ImageStatistics, offers applications in imaging and image processing for the medical, pharmaceutical, manufacturing, chemical and quality assurance industries. ImaGem was created after 20 years of research done on human perception and ImageStatistics, a statistical tool developed by Dr. Lalit K. Aggarwal. ImaGem’s Systems employ advanced optics, imaging technology and proprietary software programs to automate and integrate diamond grading. In addition to evaluating the 4C’s of diamond grading, ImaGem also analyzes Light behavior information based on precise and repeatable measures; three complementary dimensions of brilliance, intensity and sparkle. ImaGem has created a system of uniquely identifying and registering (fingerprinting) a stone without any need for laser inscription. By offering all this information, ImaGem has promoted decision-making and efficiency in the gem industry supply chain. In 1998, ImaGem Inc. was incorporated in the state of Pennsylvania, USA after funding from a major retailer, Ben Franklin Technology Partnership, and private funding. The company has developed an integrated technology to collect image data for diamonds and gemstones, analyze it using direct measurement methodology and grade for precise and repeatable measurements.
The Jonker diamond was found at the Elandsfontein mine in South Africa by Johannes Jacobus Jonker on 17 January 1934. The diamond was 726 carats, which at the time was the fourth largest uncut gem ever found.
The Empress Eugénie Diamond is an oval-shaped brilliant diamond, perfectly cut, and weighing 51 carats. It is named for the French empress Eugénie de Montijo, who owned it in the late 19th century. It is currently in the hands of a private collector.
The English Dresden is a famous diamond found at the Bagagem mines in Minas Gerais in Brazil, in 1857 at about the same time as the equally celebrated Star of the South. It was a part separated by cleavage from a larger mass, and in the rough weighed 119.5 carats. What exactly became of the remaining portion is unknown, though Mr. Dresden suggests that it may have either been destroyed when taking it from the rock, or may have remained behind in its former itacolumite matrix.
