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Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form of carbon, but diamond converts to it extremely slowly. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.
Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.
A gemstone is a piece of mineral crystal which, in cut and polished form, 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.
The Hope Diamond is a 45.52-carat (9.104 g) diamond originally extracted in the 17th century from the Kollur Mine in Guntur, India. It is blue in color due to trace amounts of boron. Its exceptional size has revealed new information about the formation of diamonds.
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.
The Cullinan Diamond is the largest gem-quality rough diamond ever found, weighing 3,106.75 carats (621.35 g), discovered at the Premier No.2 mine in Cullinan, South Africa, on 26 January 1905. It was named after Thomas Cullinan, the owner of the mine. In April 1905, it was put on sale in London, but despite considerable interest, it was still unsold after two years. In 1907, the Transvaal Colony government bought the Cullinan and Prime Minister Louis Botha presented it to Edward VII, King of the United Kingdom, who had it cut by Joseph Asscher & Co. in Amsterdam.
A diamond cut is a style or design guide used when shaping a diamond for polishing such as the brilliant cut. Cut does not refer to shape, but the symmetry, proportioning and polish of a diamond. The cut of a diamond greatly affects a diamond's brilliance; this means if it is cut poorly, it will be less luminous.
A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice. Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value. For example, most white diamonds are discounted in price when more yellow hue is detectable, while intense pink diamonds or blue diamonds can be dramatically more valuable. Of all colored diamonds, red diamonds are the rarest. The Aurora Pyramid of Hope displays a spectacular array of naturally colored diamonds, including red diamonds.
The De Beers Centenary Diamond is, at 273.85 carats (54.770 g), the third-largest diamond to have been produced in the Premier Mine. Among top-color diamonds, only the Cullinan I and II are larger than the Centenary diamond. The Centenary Diamond is rated in color as grade D color by the Gemological Institute of America, which is the highest grade of colourless diamond and is internally and externally flawless. It was named the Centenary Diamond as it was presented in the rough for the Centennial Celebration of De Beers Consolidated Mines on 11 May 1988. The Centenary Diamond was unveiled in final form in May 1991.
The Great Chrysanthemum Diamond is a famous diamond measuring 104.15 carats with a pear-shaped modified brilliant cut, rated in colour as Fancy Orange-Brown and I1 clarity by the Gemological Institute of America. The Great Chrysanthemum is roughly the same size as the re-cut Kohinoor and almost three times the size of the Hope Diamond, The Great Chrysanthemum has the dimensions of 39.10 x 24.98 x 16.00 mm. and features 67 facets on the crown, 57 facets on the pavilion and 65 vertical facets along the girdle. The diamond, designed as a pendant, became the central focus of a necklace with 410 oval, pear-shaped, round and marquis diamonds.
The Excelsior Diamond is a gem-quality diamond, and was the largest known diamond in the world from the time of its discovery in 1893 until 1905, when the larger Cullinan Diamond was found. It was found on June 30, 1893 at the Jagersfontein Mine in South Africa, 130 kilometres south east of Kimberley whose fame as a diamond mining center always overshadowed that of Jagersfontein. It had a blue-white tint and weighed 971 old carats or 995.2 metric carats. The Excelsior rates as the fourth largest rough diamond of gem quality ever found. It was ultimately cut into ten stones weighing from 13 to 68 carats..
The Logan Sapphire is a 422.98-carat (84.596 g) sapphire from Sri Lanka. One of the largest blue faceted sapphires in the world, it was owned by Sir Victor Sassoon and then purchased by M. Robert Guggenheim as a gift for his wife, Rebecca Pollard Guggenheim, who donated the sapphire to the Smithsonian Institution in 1960. The sapphire's name is derived from Rebecca's new surname after she later married John A. Logan. It has been on display in the National Gem Collection of the National Museum of Natural History in Washington, D.C., since 1971. It is a mixed cushion-cut sapphire, approximately the size of a large chicken egg, and set in a silver and gold brooch surrounded by 20 round brilliant-cut diamonds.
The Premier Mine is an underground diamond mine owned by Petra Diamonds in the town of Cullinan, 40 kilometres (25 mi) east of Pretoria, Gauteng Province, South Africa. Established in 1902, it was renamed the Cullinan Diamond Mine in November 2003 in celebration of its centenary. The mine is a carrot-shaped volcanic pipe and has a surface area of 32 hectares. The mine rose to prominence in 1905, when the Cullinan Diamond – the largest rough diamond of gem quality ever found – was discovered there.
Harry Winston was an American jeweler. He donated the Hope Diamond to the Smithsonian Institution in 1958 after owning it for a decade. He also traded the Portuguese Diamond to the Smithsonian in 1963 in exchange for 3,800 carats of small diamonds.
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. "Gabi" Tolkowsky known for cutting the famous Centenary Diamond, is one of the world's most renowned diamond cutters. Known as the father of the modern round brilliant diamond cut. and the great nephew of Marcel Tolkowsky, 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.
Graff is a British multinational jeweller based in London. It was founded by British jeweller Laurence Graff in 1960. A vertically integrated company, Graff operations comprise the design, manufacture and retail distribution of jewellery and watches.
Larisa Popova is an Italian gemologist, appraiser and jeweler.
References
- 1 2 "The Enigma: Billion-year-old black diamond sold for £3.16m". BBC. Retrieved 2022-02-12.
- ↑ "Largest cut Fancy Black (diamond)". Guinness World Records. Retrieved 2022-01-31.
- 1 2 Jani-Friend, Isabelle. "A 555.55-carat black diamond believed to come from space is going on sale". CNN. Retrieved 2022-01-31.