Nebraska State Mineral
Throughout the ages, humans have cherished gold. Many have had a compelling desire to amass great quantities of it—so compelling a desire, in fact, that the frantic need to seek and hoard gold has been aptly named "gold fever."
Gold is called a "noble" metal, an alchemical term, because it does not oxidize under ordinary conditions. In pure form, gold has a metallic luster and is sun yellow, but mixtures of gold with other metals, such as silver, copper, nickel, platinum, palladium, tellurium, and iron, create various color hues ranging from silver-white to green and orange-red. Traces of silver normally occur in natural gold, and some copper and iron may also be present. Pure gold is relatively soft—it has about the hardness of a penny. It is the most malleable and ductile of metals.
The degree of purity of native gold, bullion (bars or ingots of unrefined gold), and refined gold is stated in terms of gold content. "Fineness" defines gold content in parts per thousand. For example, a gold nugget containing 885 parts of pure gold and 115 parts of other metals, such as silver and copper, would be considered 885-fine. "Karat" indicates the proportion of solid gold in an alloy based on a total of 24 parts. Thus, 14-karat (14K) gold indicates a composition of 14 parts of gold and 10 parts of other metals. Because gold is easily bent, it is alloyed with other minerals for use in jewelry. "Karat" should not be confused with "carat," a unit of weight used for precious stones.
When gold was discovered in the Black Hills, a trail quickly developed to get the mineral from South Dakota to the railroad in Sidney, Nebraska. Today, a highway nicknamed the Gold Rush Byway parallels this route, running through Nebraska’s panhandle and the Nebraska National Forest. Since gold reflects the state’s past and present, the mineral, although not an official state symbol, represents Nebraska’s history, geology, culture, and heritage.
Gold is also the official state mineral of California and Alaska.
The word "gold" was initially an Old English word. The chemical symbol for gold, Au,is derived from the Latin word aurum, which means "shining dawn."
FORMATION AND OCCURRENCE
Gold is relatively scarce in the Earth, but it occurs in many different kinds of rocks and in many different geological environments. Furthermore, it is concentrated by geologic processes to form commercial deposits of two principal types: lode (primary) deposits and placer (secondary) deposits.
Gold occurs in hydrothermal veins and placer deposits in significant amounts. It is also found in granite and similar high-silica rocks, in contact metamorphic deposits, and in hypothermal deposits. The mineral is commonly found in quartz veins, or as grains, nuggets, or flakes in placer deposits, and in streams and rivers.
In gold-bearing country, prospectors look for gold where coarse sands and gravel have accumulated and "black sands" have concentrated and settled with the gold. Magnetite is the most common mineral in black sands, but other heavy minerals such as cassiterite, monazite, ilmenite, chromite, platinum-group metals, and some gem stones may be present.
About 45 to 50 percent of the world’s total gold production has been from the Witwatersrand District in South Africa. The city of Johannesburg was founded due to the South African gold rush. This country had been the world’s largest gold producer since 1905; in 2007, China took this title from South Africa. The largest gold mine in the United States is the Homestake Mine at Lead, South Dakota.
The great difference in density between impure gold and its host rock enables gold to be concentrated by gravity and permits the separation of gold from clay, silt, sand, and gravel by various agitating and collecting devices such as the gold pan, rocker, and sluice box.
There are many important deposits of gold throughout the world; the following is a list of localities for fine specimens.
Gold has served as a symbol of wealth throughout history. Artisans of ancient civilizations used gold lavishly in decorating tombs and temples. Gold objects made more than 5,000 years ago have been found in Egypt; particularly noteworthy are the gold items discovered by Howard Carter and Lord Carnarvon in 1922 in the tomb of Tutankhamun. This young pharaoh ruled Egypt in the 14th century BCE. An exhibit of some of these items, called "Treasures of Tutankhamun", attracted more than six million visitors in six cities during a tour of the United States from 1977 to 1979. The graves of nobles at the ancient Citadel of Mycenae near Nauplion, Greece, discovered by Heinrich Schliemann in 1876, yielded a great variety of gold figurines, masks, cups, diadems, and jewelry, plus hundreds of decorated beads and buttons. These elegant works of art were created by skilled craftsmen more than 3,500 years ago.
The ancient civilizations appear to have obtained their supplies of gold from various deposits in the Middle East. Mines in the region of the Upper Nile near the Red Sea and in the Nubian Desert area supplied much of the gold used by the Egyptian pharaohs. When these mines could no longer meet their demands, deposits elsewhere, possibly in Yemen and southern Africa, were exploited. Artisans in Mesopotamia and Palestine probably obtained their supplies from Egypt and Arabia. Recent studies of the Mahd adh Dhahab (meaning "Cradle of Gold") mine in the present Kingdom of Saudi Arabia reveal that gold, silver, and copper were recovered from this region during the reign of King Solomon (961-922 BCE).
The gold in the Aztec and Inca treasuries of Mexico and Peru is believed to have come from Colombia, although some undoubtedly was obtained from other sources. When the Conquistadors plundered the treasuries of these civilizations, many priceless gold and silver artifacts were melted or destroyed.
Nations of the world today use gold as a medium of exchange in monetary transactions. A large part of the gold stocks of the United States is stored in the vault of the Fort Knox Bullion Depository. The depository, located about 30 miles southwest of Louisville, Kentucky, is under the supervision of the director of the U.S. Mint.
In addition to monetary uses, gold is used extensively in jewelry, especially in wedding bands, as well as in decorative objects. Because it is a good conductor of electricity and heat and is malleable and stable, gold is utilized in electrical and electronic applications, dentistry, the aircraft-aerospace industry, photographic processes, other arts, and the medical, materials science, and chemical fields. Gold is also being studied for use in cancer treatment.
Danziger Goldwasser, an herbal liqueur from Gdansk, Poland, has small flakes of 22- or 23-karat gold floating in it. The liqueur has been produced since at least 1598, when alchemy was extremely popular. It was also believed that gold had beneficial medical properties. Goldschläger, an Italian cinnamon schnapps, also contains small flakes of 22-karat gold. Gold is harmless to the body, and it imparts no taste or nutritional value to the beverage.
India purchases approximately 25 percent of the world’s gold, making the world’s largest democracy also the world’s largest consumer and importer of gold.
Gold is associated with the 50th, or golden, wedding anniversary. Gold medals and statues mark achievement in sports and the arts. Examples include the gold medals of the Olympic Games, the Academy Award, and the Palme d’Or, the highest prize awarded at the Cannes Film Festival.
Marcasite, chalcopyrite, and pyrite are sometimes known as "fool’s gold."
Gold-filled, rolled gold, and gold overlay jewelry is made of a base of a non-precious metal covered with a layer of 10- or 14-karat solid gold. Gold-plated items are made of a similar base of non-precious metal, but covered in a very thin layer of gold that can wear off easily. The gold on gold-filled jewelry is about 100 times thicker than that of gold-plated jewelry, making the latter a less expensive alternative.
Group: Transition metal
Chemical Formula: Au
Crystal Structure: Isometric
Hardness (Mohs): 2½-3
Color: Metallic yellow
Density: 15-19.3 g/cm3
Streak: Shining yellow
Cleavage: None observed
Some data courtesy of the Mineralogical Society of America
Author: World Trade Press