1800 mining equipment how 2 find gold

what were some of the tools that were used in the gold mines? | synonym

what were some of the tools that were used in the gold mines? | synonym

The Gold Rush of the 1840s ended the era of the solitary miner sitting by a stream with pan in hand. Throngs traveled to California hoping to find their fortunes. Tools were soon developed to easily extract gold from rocks and riverbeds. Many of these tools have been found in the original mines above and below ground.

Stamps were used in California gold mines around 1850. First developed in England and used by Cornish miners, stamps were heavy iron machines used to pound rocks containing gold quartz into a fine dust so the gold ore could be extracted. Small stamps were commonly powered by water wheels while larger ones ran by steam engines.

A rocker, also known as a cradle, separated gold from dirt. This tool consisted of a box for shaking dirt and water back and forth so miners could find gold fragments. A miner would load the rocker with water and soil. Another would rock the box, bucket load after bucket load, to search for signs of precious metal. About 200 buckets of dirt could be "rocked" per day.

Panning for gold was also known as "placer mining." Early miners sat by riverbeds, scooping wet soil into shallow metal pans. They swirled the pans, washing away the dirt to hopefully discover particles of gold. Though more complex equipment was eventually invented, pans were still a useful tool to distinguish gold from dirt.

Riverbeds in remote mountains contained gold-bearing gravel. Hydraulic mining was used to extract this gold from water and gravel. Gigantic floating dredges scooped up the river gravel while hydraulic cannons blasted hillsides and washed them into the streams and rivers. The first hydraulic cannon was invented by Edward Mattison in 1853. Dredges and hydraulic cannons were controversial for their impact on the ecosystems. Legal battles between miners and farmers resulted in environmental controls.

Dan Boone has been writing since 1999. His work has appeared on CaribbeanChannel.com and he wrote for the "Virgin Voice" magazine and its website, Virgin Voices. Boone has a Bachelor of Arts in composition and arranging from Berklee College of Music in Boston. He also holds a certificate in digital-sound engineering from the Trebas Institute in Montreal.

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mining 101: ultimate list of gold mining equipment - precious metal info

mining 101: ultimate list of gold mining equipment - precious metal info

Found in Bulgaria are some of the oldest gold artifacts known to mankind, in the Varna Necropolis, a collection of graves built between 4700 and 4200 BC. This finding, dating back nearly 7000 years, provides evidence of the first civilization to use gold mining equipment. Some archeologists claim the Sakdrisi site in southern Georgia, which dates to roughly 4000 BC, is the worlds first gold mine.

In the 19th century, gold rushes occurred around the globe and people migrated to different regions hoping to strike it rich. The Victorian Gold Rush took place in Victoria, Australia, between 1851 and the late 1860s, and the Second Boer War took place in South Africa between 1899 and 1902. In America, the famous California Gold Rush took place in 1949, and discovery of Nevada's Carlin Trend,North America's largest gold depository,took placein 1961.

Since the beginning of civilization, humans have mined around 6 billions troy ounces of gold. Today, 2.5 percent of all gold production happens in Nevada, making it one of the primary regions on earth. As of 2017, China produced the most gold per year at 429 metric tons, followed by Australia, and then Russia. However, there's still a lot of gold out there, and you can join in the gold mining industry by investing in basic gold mining equipment.

There are two basic steps to gold mining: prospecting and production. "Prospecting" refers to the actual search in a certain area for valuable minerals, and "production," also known as mining, is the physical act of removing the gold from where you found it. Since different equipment exists for prospecting and mining, this article explores, briefly, equipment used for prospecting, and then focuses, primarily, on gold mining equipment.

How do you find gold? In the gold mining industry, theres a lot of value in learning from others who have gone before you. No one ever gets all the gold out of any one location. So, try going to where gold exists in abundance. Consider this: the California Gold Rush only removed a small percentage of the gold thats out there. That's right.

There are areas in California that are still open to recreational prospecting, including the Auburn State Recreation Area and the South Yuba Recreation lands. Once you get your feet wet in an area proven to have gold, you can move on to other areas closer to home. After mastering prospecting and gold-mining techniques, you might even want to look for gold in your own back yard.

Some people say, Gold is where you find it. What this means is you have to learn what to look for. First, understand that the way water moves in rivers and streams determines where gold deposits might settle. Next, you need to learn why gold concentrates in certain areas, and then search those areas.

Once youve selected a specific waterway for mining, youll want to pick specific points to search. Since it is impractical to search the entire stream or river, there are ways to read a waterway to determine the most likely places to find gold. The following describes how to find those places.

The first thing to know is gold is heavy. Its about 19 times heavier than the same amount of water and 6 times heavier than solid material found in streams and rivers. So, anything that slows the movement of water is likely to trap gold deposits. Things that slow down moving water are:

Water on the downriver side of obstacles will move slower, and this is where heavier gold will settle. When looking at a chosen waterway, begin by searching for natural dams where gold may have collected. Another place that collects heavier objects in a waterway is inside bends, places where water naturally slows down. Heavy objects will often form a bar at these points, and the upside of a bar inside bends is a great place to look for gold.

Once gold has settled in a stream, over time, it works its way down layers of soil and settles in bedrock. A great location for gold is in the material coating bedrock under a stream. Choose a location on the inside a bend where there is an obstruction and then dig to the bedrock. Sifting the soil coating bedrock, usually, will produce gold.

Learn to delay the excitement of seeing gold for the first time and you will have more gold-filled dirt to take home with you. Once you get better at choosing locations, and especially if you find a proven location, its best to spend your time digging and removing dirt, rather than sifting and cleaning it on site. Delay celebrating and get as much dirt as possible to take home. Once you get home, sift and clean the gold youve found.

Another great place to look for gold is in tall grass growing above an inside bend. Grass acts like a sieve and the largest gold pieces end up at the roots of grass. They often call this kind of gold oat gold. The pieces might be smaller than gold found in other places, but there could be a lot.

If you want to invest a little in your endeavor, you can purchase a metal detector designed to find gold. This gold mining equipment can cut down on the time spend hunting, but a mid-level detector can cost about $600.

When considering getting involved in gold prospecting and mining, make sure you learn and follow the rules. There are certain places where prospecting is legal and others where it is not. Many prospecting clubs exist and joining one can help ensure you are following rules. For examples, most sites require that you refill any holes you have dug, and that you do not destroy local plant life. Learn the rules before you head out with your gold mining equipment.

Once youve finished prospecting and have a location where you know there is gold, you will need gold mining equipment. What you use will depend on the size of your operation. If you are working in the gold industry, you will have industrial gold mining equipment. If you are mining on your own as a hobby, youll need smaller, personal gold mining equipment. Lets look at both.

If you want to use industrial mining equipment, make sure you have the proper training. If working for a business, they should provide needed training. However, if you purchased industrial gold mining equipment for a personal claim, be certain you know what you are doing. Safety should always come first.

Miners use drills for underground mining to create access holes for descending underground, or to place explosive charges to bring material to the surface. The drill miners choose depends on how and what is being mined.

Blasting tools create an explosion to blast away chunks of material to access minerals. Blasting can also remove chunks of unwanted materials that are keeping other machines or people from getting to a seam of wanted materials. In underground and open pit mines, miners use both drilling and blasting tools, often together. They use drills to place blasting tools at the right depth and in the right place.

Earth-moving machines move around large amounts of materials. They might haul material after blasting, move other materials allowing access to seams of minerals, dig underground mines, or get down to the bedrock where minerals might exist.

Crushing equipment moves materials around an underground mine. Miners use this equipment to keep the flow of materials going at an efficient rate, and to save money. It is easier to remove crushed rocks rather than heavy chunks, so crushing equipment saves time and effort.

A sluice box is a way to sift through raw material more quickly. Essentially, its automated panning. These machines used to be large and heavy in the early days of panning, but are now lightweight and easier to use. If youre serious about mining, they are worth checking out.

A higher quality sluice box, high banker boxes have a water pump allowing more material to move through faster. These boxes recycle water so you dont have to rely on water flow in the river. They recover more gold than basic models.

If you arent going into the professional gold mining industry, but are looking for a hobby or a part-time job to bring in a little extra money, consider joining a mining club to help you once you begin your prospecting journey. The club will help you learn about personal gold mining equipment, but, for now, lets take a quick look at what you will need.

There are lots of different sizes, colors, and options in gold pans. Essentially, a 14-inch plastic pan is the best size, by far. Color does not matter, however gold shows up better in black. Black sand shows up better in blue or green. There are many new kinds of pans, but a basic pan with sharp, undercut riffles is all you need. Make sure the bottom of the pan is as wide as possible to catch more gold.

You will need a place to store the gold you find. All you need is a waterproof container you can close tightly, such as a 35mm film container. You can purchase containers on the internet, specifically made for holding gold.

The last thing to consider is investing in Gold Lab, a personal system that recovers gold from the concentrate you have refined. A good gold panner can get most of the gold from refined dirt, but a Gold Lab kit will allow you to further refine and recover 100% of your gold.

Once you have your equipment, its time to get in the river to pan for gold. This simple technique mimics what the river does naturally. You recover material, or dirt and place it in the pan, from a river location where you think there might be gold. Then, you shake it in a left-to-right motion underwater to sweep away light materials while causing heavier materials to go to the bottom of the pan.

Take the pan with the riffles on the far side and shake it, vigorously, left and right. This breaks up materials sending heavier items to the bottom. Do not slosh water out of the pan. If you need to, repeat the previous step and break up larger chunks again.

Continue shaking the pan back and forth and keep removing the top layer of lighter materials until you are down to only the heaviest materials, such as coins, BBs, old bullets, buckshot, nails, garnets, black iron rocks and black sand. You should now be able to see gold in the pan when shaking and tilting it forward slightly.

Use a magnet to remove black sand and other metal objects. Keep removing things until only gold remains. Remove the larger gold pieces and save any leftover concentrate. Let it sit for a while so you can recover any remaining pieces of gold that settle.

If you have enjoy the outdoors, and have just a little ambition, you can make a hobby out of gold prospecting and mining. All you need are basic tools that as your gold mining equipment and the willingness to do a little research. Once you decide where to go, or join a mining club to help you find locations, pack up your tools and prospect. It may take practice at panning before you find anything, but once you do, youll love the feeling of satisfaction and discovery. If you find you enjoy the hobby, invest in semi-professional gold mining equipment and see if you can up the amount you discover. Even if you only discover a few flakes, prospecting can be a great way to make new friends, learn about the gold industry, and understand a little about gold prospectors of old. Its an inexpensive hobby, so grab basic gold mining equipment and get started today.

911MPE has for target market what mining professionals consider the pilot-plant scale mining operation or artisanal mining operations with a focus around under 500TPD. Metals you can extract include: gold, silver or other of the precious group as well as the classic base metals; copper, lead, zinc, nickel, molybdenum. Much of our ultra-small scale equipment allows you to process from just a few kilo (pounds) per day and work on your passion for a small budget.

early gold mining methods

early gold mining methods

The gold panner patiently crouching alongside a river is symbolic of the Gold Rush, and yet gold pans were probably the most ineffective of all the miners tools, even though that is what most miners used early on. As word leaked out in 1848 about gold in the Sierra Nevada foothills, early-day entrepreneur Sam Brannan cornered the California market on pans, picks and shovels. Without lifting a finger to do any gold mining of his own, he became Californias first millionaire by catering to the needs of the miners. Miners who couldnt find pans made do with kitchen bowls or whatever they could find.

Although gold pans were much in evidence during the early days of the Gold Rush, miners used them less and less as time went on and they created better gold extraction devices. Even today, however, some gold seekers will use the light and simple pans for prospecting, systematically sampling gravels as they work up a stream, for example, and knowing that when the gold color stops, a vein or two of gold feeding into the stream may be close at hand.

Another popular tool was the rocker or cradle, and indeed, this tool did vaguely resemble a childs cradle. Using a handle on the rocker to push it back and forth, the miner dumped gravel into the top part and finer and heavier particles dropped through a screen, helped along by buckets of water. The bottom part of the device had slats, or riffles, that caught the heavier metals. After many shovel loads of gravel were pushed through the rocker, the miner would then use his gold pan to sort out the heavy minerals and, with luck, find gold.

The long tom was similar in theory to the rocker but was much more elaborate. A paddlewheel ensured a constant source of water. Again gravel was shoveled into the top end and the water pushed it along a long wooden course, sometimes hundreds of feet long. Again, the slats collected the heavier ore, which was then further processed.

For these early techniques, water was an essential part of the process. However, since gold was not always found next to streams, miners often had to get the water to where the gold was, and thus elaborate networks of mining ditches were built throughout the gold country; remnants of these ditches can be found even today, and now some are used for agriculture.

Miners from Sonoran Mexico had a technique for pulverizing gold ore that required no water for the initial stages of gold processing. Called the arrastre, this system consisted of an upright axle with large spokes. Horses or mules, hooked to the outside edges of the spokes, pulled them around and around. Tied to the interior of the spokes were chunks of gold bearing quartz, which were dragged over a rocky surface and hence pulverized. After the rock was pulverized, the miners then used gold pans for final processing.

As time went on, gold mining became increasingly more sophisticated. The solitary gold miner of the 1840s gave way to hundreds of miners toiling in deep hard rock mines, such as those found in Jackson and Grass Valley. In other areas, such as Malakoff Diggins, huge hydraulic hoses washed away entire mountainsides in the search for gold. In the flatlands, massive dredgers processed gravels from ancient riverbeds; evidence of this kind of mining can still be found, for example, in and around Folsom, where miles of dredger rockpiles still exist. Ore crushing went well beyond the simple arrastre with the proliferation of stamp mills large and small. The din of these machines could be overwhelming as they pounded quartz into fine rubble. One of the last working stamp mills is demonstrated annually at Founders Day in Georgetown, California.

Although a few working mines still exist, little gold mining takes place today in California. On the rivers where this kind of activity is permitted, divers using portable dredges make a hobby of sucking out gold from river-bottom crevices.

These days, no one is going to get rich gold panning. The easy gold is long gone. But its still fun to slosh a few pans of gravel to see if any color is there. Many hardware stores throughout the gold country still sell gold pans. One never knows. As many a veteran goldseeker will attest, Gold is where you find it.

gold: history of use, mining, prospecting, assay & production

gold: history of use, mining, prospecting, assay & production

Egyptian gold: Artisans of ancient civilizations used gold lavishly in decorating tombs and temples, and gold objects made more than 5,000 years ago have been found in Egypt. Image copyright iStockphoto / Akhilesh Sharma.

Gold was among the first metals to be mined because it commonly occurs in its native form, that is, not combined with other elements, because it is beautiful and imperishable, and because exquisite objects can be made from it. Artisans of ancient civilizations used gold lavishly in decorating tombs and temples, and 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 B.C. An exhibit of some of these items, called "Treasures of Tutankhamun," attracted more than 6 million visitors in six cities during a tour of the United States in 1977-79.

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 B.C.).

The gold in the Aztec and Inca treasuries of Mexico and Peru believed to have come from Colombia, although some undoubtedly was obtained from other sources. The Conquistadores plundered the treasuries of these civilizations during their explorations of the New World, and many gold and silver objects were melted and cast into coins and bars, destroying the priceless artifacts of the Indian culture.

Gold coin: As a highly valued metal, gold was used as a financial standard and has been used in coinage for thousands of years. United States ten dollar gold coin from 1850. Image copyright iStockphoto / Brandon Laufenberg.

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 Mint.

Gold in the Depository consists of bars about the size of ordinary building bricks (7 x 3 5/8 x 1 3/4 inches) that weigh about 27.5 pounds each (about 400 troy ounces; 1 troy ounce equals about 1.1 avoirdupois ounces.) They are stored without wrappings in the vault compartments.

Aside from monetary uses, gold, like silver, is used in jewelry and allied wares, electrical-electronic applications, dentistry, the aircraft-aerospace industry, the arts, and medical and chemical fields.

The changes in demand for gold and supply from domestic mines in the past two decades reflect price changes. After the United States deregulated gold in 1971, the price increased markedly, briefly reaching more than $800 per troy ounce in 1980. Since 1980, the price has remained in the range of $320 to $460 per troy ounce. The rapidly rising prices of the 1970's encouraged both experienced explorationists and amateur prospectors to renew their search for gold. As a result of their efforts, many new mines opened in the 1980's, accounting for much of the expansion of gold output. The sharp declines in consumption in 1974 and 1980 resulted from reduced demands for jewelry (the major use of fabricated gold) and investment products, which in turn reflected rapid price increases in those years.

Gold is called a "noble" metal (an alchemistic term) because it does not oxidize under ordinary conditions. Its chemical symbol Au is derived from the Latin word "aurum." In pure form gold has a metallic luster and is sun yellow, but mixtures of other metals, such as silver, copper, nickel, platinum, palladium, tellurium, and iron, with gold create various color hues ranging from silver-white to green and orange-red.

Pure gold is relatively soft--it has about the hardness of a penny. It is the most malleable and ductile of metals. The specific gravity or density of pure gold is 19.3 compared to 14.0 for mercury and 11.4 for lead.

Impure gold, as it commonly occurs in deposits, has a density of 16 to 18, whereas the associated waste rock (gangue) has a density of about 2.5. The difference in density 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 sluicebox.

Mercury (quicksilver) has a chemical affinity for gold. When mercury is added to gold-bearing material, the two metals form an amalgam. Mercury is later separated from amalgam by retorting. Extraction of gold and other precious metals from their ores by treatment with mercury is called amalgamation. Gold dissolves in aqua regia, a mixture of hydrochloric and nitric acids, and in sodium or potassium cyanide. The latter solvent is the basis for the cyanide process that is used to recover gold from low-grade ore.

Hydraulic placer mining at Lost Chicken Hill Mine, near Chicken, Alaska. The firehose blasts the sediment outcrop, washing away sand, clay, gravel and gold particles. The material is then processed to remove the gold. USGS image.

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. Incidentally, 14K gold is commonly used in jewelry manufacture. "Karat" should not be confused with "carat," a unit of weight used for precious stones.

The basic unit of weight used in dealing with gold is the troy ounce. One troy ounce is equivalent to 20 troy pennyweights. In the jewelry industry, the common unit of measure is the pennyweight (dwt.) which is equivalent to 1.555 grams.

The term "gold-filled" is used to describe articles of jewelry made of base metal which are covered on one or more surfaces with a layer of gold alloy. A quality mark may be used to show the quantity and fineness of the gold alloy. In the United States no article having a gold alloy coating of less than 10-karat fineness may have any quality mark affixed. Lower limits are permitted in some countries.

No article having a gold alloy portion of less than one-twentieth by weight may be marked "gold-filled," but articles may be marked "rolled gold plate" provided the proportional fraction and fineness designations are also shown. Electroplated jewelry items carrying at least 7 millionths of an inch (0.18 micrometers) of gold on significant surfaces may be labeled "electroplate." Plated thicknesses less than this may be marked "gold flashed" or "gold washed."

Gold sluice: Portable gold sluice. Miners place the sluice in the stream and dump sediments in the upstream side. The current transports the sediments through the sluice and the heavy gold particles become lodged in the sluice. One miner can process a lot more sediment through a sluice than through a gold pan. Image copyright iStockphoto / LeeAnn Townsend.

Gold is relatively scarce in the earth, but it occurs in many different kinds of rocks and in many different geological environments. Though scarce, gold is concentrated by geologic processes to form commercial deposits of two principal types: lode (primary) deposits and placer (secondary) deposits.

Lode deposits are the targets for the "hardrock" prospector seeking gold at the site of its deposition from mineralizing solutions. Geologists have proposed various hypotheses to explain the source of solutions from which mineral constituents are precipitated in lode deposits.

One widely accepted hypothesis proposes that many gold deposits, especially those found in igneous and sedimentary rocks, formed from circulating groundwaters driven by heat from bodies of magma (molten rock) intruded into the Earth's crust within about 2 to 5 miles of the surface. Active geothermal systems, which are exploited in parts of the United States for natural hot water and steam, provide a modern analog for these gold-depositing systems. Most of the water in geothermal systems originates as rainfall, which moves downward through fractures and permeable beds in cooler parts of the crust and is drawn laterally into areas heated by magma, where it is driven upward through fractures. As the water is heated, it dissolves metals from the surrounding rocks. When the heated waters reach cooler rocks at shallower depths, metallic minerals precipitate to form veins or blanket-like ore bodies.

Another hypothesis suggests that gold-bearing solutions may be expelled from magma as it cools, precipitating ore materials as they move into cooler surrounding rocks. This hypothesis is applied particularly to gold deposits located in or near masses of granitic rock, which represent solidified magma.

A third hypothesis is applied mainly to gold-bearing veins in metamorphic rocks that occur in mountain belts at continental margins. In the mountain-building process, sedimentary and volcanic rocks may be deeply buried or thrust under the edge of the continent, where they are subjected to high temperatures and pressures resulting in chemical reactions that change the rocks to new mineral assemblages (metamorphism). This hypothesis suggests that water is expelled from the rocks and migrates upwards, precipitating ore materials as pressures and temperatures decrease. The ore metals are thought to originate from the rocks undergoing active metamorphism.

The primary concerns of the prospector or miner interested in a lode deposit of gold are to determine the average gold content (tenor) per ton of mineralized rock and the size of the deposit. From these data, estimates can be made of the deposit's value. One of the most commonly used methods for determining the gold and silver content of mineralized rocks is the fire assay. The results are reported as troy ounces of gold or silver or both per short avoirdupois ton of ore or as grams per metric ton of ore.

Gold dredge: A scuba diver vacuums sediment to be processed by a portable gold dredge. Scuba gear allows the prospector to carefully get access to cracks and crevices on the stream bed where gold nuggets might be lodged. Image copyright iStockphoto / Gary Ferguson.

Gold is extremely resistant to weathering and, when freed from enclosing rocks, is carried downstream as metallic particles consisting of "dust," flakes, grains, or nuggets. Gold particles in stream deposits are often concentrated on or near bedrock, because they move downward during high-water periods when the entire bed load of sand, gravel, and boulders is agitated and is moving downstream. Fine gold particles collect in depressions or in pockets in sand and gravel bars where the stream current slackens. Concentrations of gold in gravel are called "pay streaks."

Gold drywasher: A portable dry washer used to sift gold nuggets from soil where water is not available. Soil is dumped into the top pan and is shaken through the bottom pan. Heavy gold nuggets are mechanically separated from lighter materials. Image copyright iStockphoto / Arturo M. Enriquez.

In gold-bearing country, prospectors look for gold where coarse sands and gravel have accumulated and where "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 gemstones may be present.

Placer deposits have formed in the same manner throughout the Earth's history. The processes of weathering and erosion create surface placer deposits that may be buried under rock debris. Although these "fossil" placers are subsequently cemented into hard rocks, the shape and characteristics of old river channels are still recognizable.

The content of recoverable free gold in placer deposits is determined by the free gold assay method, which involves amalgamation of gold-bearing concentrate collected by dredging, hydraulic mining, or other placer mining operations. In the period when the price of gold was fixed, the common practice was to report assay results as the value of gold (in cents or dollars) contained in a cubic yard of material. Now results are reported as grams per cubic yard or grams per cubic meter.

Through laboratory research, the U.S. Geological Survey has developed new methods for determining the gold content of rocks and soils of the Earth's crust. These methods, which detect and measure the amounts of other elements as well as gold, include atomic absorption spectrometry, neutron activation, and inductively coupled plasma-atomic emissionon spectrometry. These methods enable rapid and extremely sensitive analyses to be made of large numbers of samples.

Gold was produced in the southern Appalachian region as early as 1792 and perhaps as early as 1775 in southern California. The discovery of gold at Sutter's Mill in California sparked the gold rush of 1849-50, and hundreds of mining camps sprang to life as new deposits were discovered. Gold production increased rapidly. Deposits in the Mother Lode and Grass Valley districts in California and the Comstock Lode in Nevada were discovered during the 1860's, and the Cripple Creek deposits in Colorado began to produce gold in 1892. By 1905 the Tonopah and Goldfield deposits in Nevada and the Alaskan placer deposits had been discovered, and United States gold production for the first time exceeded 4 million troy ounces a year--a level maintained until 1917.

During World War I and for some years thereafter, the annual production declined to about 2 million ounces. When the price of gold was raised from $20.67 to $35 an ounce in 1934, production increased rapidly and again exceeded the 4-million-ounce level in 1937. Shortly after the start of World War II, gold mines were closed by the War Production Board and not permitted to reopen until 1945.

From the end of World War II through 1983, domestic mine production of gold did not exceed 2 million ounces annually. Since 1985, annual production has risen by 1 million to 1.5 million ounces every year. By the end of 1989, the cumulative output from deposits in the United States since 1792 reached 363 million ounces.

Consumption of gold in the United States ranged from about 6 million to more than 7 million troy ounces per year from 1969 to 1973, and from about 4 million to 5 million troy ounces per year from 1974 to 1979, whereas during the 1970's annual gold production from domestic mines ranged from about 1 million to 1.75 million troy ounces. Since 1980 consumption of gold has been nearly constant at between 3 and 3.5 million troy ounces per year. Mine production has increased at a quickening pace since 1980, reaching about 9 million troy ounces per year in 1990, and exceeding consumption since 1986. Prior to 1986, the balance of supply was obtained from secondary (scrap) sources and imports. Total world production of gold is estimated to be about 3.4 billion troy ounces, of which more than two-thirds was mined in the past 50 years. About 45 percent of the world's total gold production has been from the Witwatersrand district in South Africa.

The largest gold mine in the United States is the Homestake mine at Lead, South Dakota. This mine, which is 8,000 feet deep, has accounted for almost 10 percent of total United States gold production since it opened in 1876. It has combined production and reserves of about 40 million troy ounces.

In the past two decades, low-grade disseminated gold deposits have become increasingly important. More than 75 such deposits have been found in the Western States, mostly in Nevada. The first major producer of this type was the Carlin deposit, which was discovered in 1962 and started production in 1965. Since then many more deposits have been discovered in the vicinity of Carlin, and the Carlin area now comprises a major mining district with seven operating open pits producing more than 1,500,000 troy ounces of gold per year.

About 15 percent of the gold produced in the United States has come from mining other metallic ores. Where base metals- -such as copper, lead, and zinc--are deposited, either in veins or as scattered mineral grains, minor amounts of gold are commonly deposited with them. Deposits of this type are mined for the predominant metals, but the gold is also recovered as a byproduct during processing of the ore. Most byproduct gold has come from porphyry deposits, which are so large that even though they contain only a small amount of gold per ton of ore, so much rock is mined that a substantial amount of gold is recovered. The largest single source of byproduct gold in the United States is the porphyry deposit at Bingham Canyon, Utah, which has produced about 18 million troy ounces of gold since 1906.

Geologists examine all factors controlling the origin and emplacement of mineral deposits, including those containing gold. Igneous and metamorphic rocks are studied in the field and in the laboratory to gain an understanding of how they came to their present location, how they crystallized to solid rock, and how mineral-bearing solutions formed within them. Studies of rock structures, such as folds, faults, fractures, and joints, and of the effects of heat and pressure on rocks suggest why and where fractures occurred and where veins might be found. Studies of weathering processes and transportation of rock debris by water enable geologists to predict the most likely places for placer deposits to form. The occurrence of gold is not capricious; its presence in various rocks and its occurrence under differing environmental conditions follow natural laws. As geologists increase their knowledge of the mineralizing processes, they improve their ability to find gold.

gold rush prospector old pictures: miner, 49er panning photos

gold rush prospector old pictures: miner, 49er panning photos

Gold prospecting sure has changed over the last few hundred years. During the great gold rushes in the United Stateswhich took place in the 1800s and early 1900s and were photographed extensivelyminers and prospectors in search of gold traveled across the country to places like Georgia, California, Colorado, Alaska and other states with hopes of striking it rich.

These original gold rush prospectorsof whom the California forty-niners were the most famousoften didnt have anything more than rudimentary panning and prospecting equipment, as you can see in many old pictures. They set out in small teams in the wilderness with only a donkey or mule, a pick, a shovel, a gold pan and perhaps some sluicing equipment. They were real pioneers, and very few of them ever ended up finding the fortune in gold nuggets and flakes that they had dreamed of.

From the cold and snowy climate of Alaska, the Klondike and the Yukon to the wilderness of California, these original prospectors have earned a respected place in American history. The classic black-and-white photos of grizzled old gold miners and prospectors from the 19th and early 20th century have earned a place in our collective culture.

Below are some of the most famous and interesting photographs from this era, showing young and old gold prospectors and miners looking for gold in many different states. These pictures will always be an important part of U.S.A. history, especially since many of our most successful and populous states saw their original population boom due to local gold rushes. Remember that when you look at some of these old pictures of gold prospectors and 49ers, youre looking back at history that help formed the society that you would someday live in.

the old ways: the monster gold dredges multi-story machines built in the first half of the 1900s

the old ways: the monster gold dredges multi-story machines built in the first half of the 1900s

The original gold dredges were large, multi-story machines built in the first half of the 1900s.Small suction machines are currently marketed as gold dredges to individuals seeking gold: just offshore from the beach of Nome, Alaska, for instance.

The material is then sorted/sifted using water. On large gold dredges, the buckets dump the material into a steel rotating cylinder (a specific type of trommel called the screen) that is sloped downward toward a rubber belt (the stacker) that carries away oversize material (rocks) and dumps the rocks behind the dredge.

The cylinder has many holes in it to allow undersized material (including gold) to fall into a sluice box. The material that is washed or sorted away is called tailings. The rocks deposited behind the dredge (by the stacker) are called tailing piles. The holes in the screen were intended to screen out rocks (e.g., 3/4 inch holes in the screen sent anything larger than 3/4 inch to the stacker).

The basic concept of retrieving gold via placer mining has not changed since antiquity. The concept is that the gold in sand or soil will settle to the bottom because gold is heavy/dense, and dirt, sand and rock will wash away, leaving the gold behind. The original methods to perform placer mining involved gold panning, sluice boxes, and rockers. Each method involves washing sand, gravel and dirt in water. Gold then settles to the bottom of the pan, or into the bottom of the riffles of the sluice box.

The gold dredge is the same concept but on a much larger scale.Gold dredges are an important tool of gold miners around the world.They allow profitable mining at relatively low operational costs. Even though the concept is simple in principle, dredges can be engineered in different ways allowing to catch different sizes of gold specimen. Hence the efficiency of gold dredges differs greatly depending on its specifications.

By the mid to late 1850s the easily accessible placer gold in California was gone, but much gold remained. The challenge of retrieving the gold took a professional mining approach to make it pay: giant machines and giant companies. Massive floating dredges scooped up millions of tons of river gravels, as steam and electrical power became available in the early 1900s.

The last giant gold dredge in California was the Natomas Number 6 dredge operating in Folsom, California ceased operations on 12 Feb 1962 as cost of operation began exceeding the value of the gold recovered.Many of these large dredges still exist today in state-sponsored heritage areas (Sumpter Valley Gold Dredge, Dredge. No. 4 National Historic Site of Canada) or tourist attractions.

Photos: Historic Chatanika Gold Dredge No. 3 The historic Chatanika Gold Dredge No. 3, outside Fairbanks, burned in August 2013, destroying the wood and metal structure. But its story isnt over yet. Courtesy Jane Haigh

In the late 1990s and through today, dredging has returned as a popular form of gold mining. Advances in technology allow a small dredge to be carried by a single person to a remote location and profitably process gravel banks on streams that previously were inaccessible to the giant dredges of the 1930s.Today dredges are versatile and popular consisting of both floating surface dredges that use a vacuum to suck gravel from the bottom and submersible dredges.In 2015 goldminer Tony Beets is reconstructing a 70-year-old dredge (as seen in the popular TV series on Discovery channel Gold Rush).

Until September 2007 this gold dredge sat alongside the Taylor Highway between Dawson City, Yukon and Tok, Alaska. Due to its deteriorating condition and safety concerns, the Bureau of Land Management (BLM) had it removed. Some major parts were set up as an interpretive display near the Chicken post office, but the majority of it went to the Tok garbage dump.

An Australian dredge. It weighed over 1000 tons (.907 tonnes) and had 63 ten cubic foot (0.28 cubic metre) buckets, each capable of gouging the alluvial gravels at the rate of 23 buckets per minute, 24 hours a day. source

The Sumpter Valley Gold Dredge is a historic gold dredge located in Sumpter, in the U.S. state of Oregon. Gold was discovered in Sumpter in 1862. Three gold dredges were put into service in the Sumpter Valley district between 1912 and 1934.

There were once three of these working the Powder River, this is Dredge #3. The remains of Dredge #2 can be seen on the North side of town in a pond it made, while the remains of Dredge #1 are in a pond about six miles south at what was once McEwen. Besides the tailing piles that line the river and make it look more like a series of ponds these days, one of the first sights in town is a collection of logging and mining equipment on the right side of town.

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