Several readers have inquired about locations in this area that are open to the public where they can pan for gold. One of my favorites os the Libby Creek Recreational Gold Panning Area. If you know of other locations in the Northwest, please post your comments below. Wishing you color in your pan.
The Kootenai National Forest provides an opportunity for you and your family to take part in the history of Libby through recreational gold panning at the Libby Creek Recreational Gold Panning Area.
The tumoff to Libby Creek Road is approximately 13 miles south of Libby on Highway 2. The Libby Creek Recreational Gold Panning Area is an additional 10 miles up Libby Creek Road 231. Please note that Libby Creek Road is graveled but well maintained.
There are no developed parking lots or camping facilities at the Gold Panning Area. Camping is primitive with dispersed sites. However, there is a men's and women's outhouse in the main panning area. For those planning longer visits to the area, Howard Lake Campground is one mile south of the Gold Panning Area. Howard Lake Campground, a developed fee campground next to Howard Lake, offers swimming, fishing, hiking opportunities, a water well, and toilets.
The purpose of these restrictions are for the protection of historical archaeological interest, protection of improvements, other surface resources, property, and safety.
*MOTORIZED equipment is any equipment having or using an engine, motor, or powered by electricity.
**MECHANIZED equipment is any device designed to increase production above the level obtained with gold pans and hand tools. Examples would include: Sluice Boxes, Dry Washers. Rocker Boxes, Wheelbarrows, and Metal Detectors.
The bedrock seen on the mountain peaks surrounding the Libby Creek Recreational Gold Panning Area is that of the Precambrian Belt formation. Rocks of Precambrian age, meaning older than Cambrian, are rocks at least 800 million years old. These sedimentary rocks, which are thousands of feet thick, were formed by the accumulation of mud, carbonate, silt, and sand in huge inland seas that extended for miles over what is now known as Northwest Montana and North Idaho. Low grade metamorphism altered the buried sediments to form the bedrock as it is seen today as quartzite, siltite, and argillite. The Belt rocks contain no animal fossils, but may contain fossils of primitive plants such as blue-green algae called Stromatolites. Some of the layers of rock contain ripple marks, salt casts, and mud cracks which indicate periods of wetting and drying during deposition.
The gold found in the panning area is defined as a placer deposit, meaning a place where eroded mineral particles (usually gold) have accumulated due to some form of movement such as by streams or glaciers. The gold-bearing gravels found in the Libby Creek Recreational Gold Panning Area were deposited as a result of alpine glaciation, which occurred between 10,000 and 130,000 years ago. During the Pleistocene Era, much of the Libby Creek Drainage was covered by glaciers which gouged the Belt rock off of the mountain peaks and carved out the valley bottoms. The glaciers left deposits of till, or moraines, at the edge of the retreating ice. Water from Libby Creek, Howard Creek, and other glacial melt streams reworked portions of the glacial moraine concentrating the gold in the channels of Libby Creek and in what is now known as the Libby Creek Recreational Gold Panning Area.
Any gold you happen to find is yours to keep. If you wish to sell your gold, many coin dealers and pawn shops in Montana will buy raw gold. Ask around locally or check a phone book if you are interested in selling any gold that you may find.
Placer Mining on Libby Creek
Miners began prospecting Libby Creek as early as 1864. Libby Creek was named in the 1860's by early prospector Stephen Allen, after his daughter Elizabeth or "Libby." In the summer of 1867, a party of 12 miners were prospecting upstream on Libby Creek near the Libby Creek Canyon. A party of four miners: Stephen Allen, Anthony Kavanaugh, John Moore and Joseph Herron left eight of their companions, including John Fisher, to get supplies at Spokane Bridge, Washington Territory. After returning to the Kootenai in August, they were ambushed by a small group of Kootenai Indians on Libby Creek at about one mile from the confluence of Libby Creek and the Kootenai River. Three of the four miners died during the attack. For the next 21 days, Herron, who escaped with a chest wound, hid during the day and survived on service berries. He was finally located by a party of miners who treated his wound and look him out of the area. The small group of Kootenai responsible for the killings scattered, but five were later located by miners and executed.
By September of 1867, the Montana Post reported that there were 500 to 600 miners working on Libby Creek for a short time. The mining camp established on Libby Creek was named "Libbysville". The initial excitement began to die down and only about one hundred miners were on Libby Creek in 1868. By 1876, John S. Fisher or "Jack" was the only reported miner working on the creek. The placer mining activity in this very isolated mining district seems to have ended until the mid 1880's.
The Second Rush on Libby Creek
By 1883, an outwash of miners from the Coeur d'Alene Mining District began to work their way into the Cabinet Mountains via the Vermilion River. Some sniping activity (prospecting for gold in bedrock without formal claims) was noted in 1885 on Libby Creek by Thomas Shearer. He then headed to Thompson Falls, Montana Territory where he interested miners such as B.F. Howard and Oliver Woodcoe to join him and file claims on Libby Creek. A second rush began in the area of Libby, Poorman, and Bear Creek in 1885.
Hundreds of miners were working Libby Creek during this time. However, it was interesting to note that the mining camp was so isolated that the "soiled doves" (prostitutes), which were found in other more lucrative and accessible mining camps, were not to be found in Libby Camp during the 1880's. A tent camp was established in the Libby Creek Mining District by 1886 and named "Lake City", or "Oldtown". George Good operated a store in this mining camp in 1887, which was supplied by a packstring (horses or mules) via a trail from Thompson Falls. In the spring of 1889, Planina E. Field arrived with her husband, Martin V. Field, to Libby Creek. She was the first non-native American woman in the mining district and for some years was the only woman in the mining camp. Chinese miners began to lease claims from the white miners on Libby Creek in 1887, and by 1889 there were about 25 Chinese working on the district. One night in November of 1890, a Chinese miner was allegedly seen robbing the sluice boxes of Thomas Bryan on Libby Creek. A miners' meeting ensued and the Chinese were banned from Libby Creek and given an hour to leave the camp. They left via the trail to Thompson Falls and no Chinese were allowed in the Libby Creek Mining District for many years.
The isolation of the Libby Mining District was lessened by the construction of the Great Northern Railroad into the Kootenai in 1892.
Mining has taken place in the vicinity of the Libby Creek Recreational Gold Panning Area or "gold panning area" since 1886 when placer claims were first located on upper Libby Creek and Howard Creek. Howard Creek and Howard Lake were prospected and named after the Howard brothers, Alfred and Benjamin. These two were among some of the earliest miners to file and work claims on Upper Libby Creek from 1885 and 1886. A.V. Howard worked on his claims on Libby and Howard Creeks from 1886 to the 1920's. B.F. Howard, who had arrived at Libby Creek during late summer of 1885, had a mining camp in the vicinity of Ramsey Creek. He mined on Libby creek until his death in 1915 at the age of 80.
Mining activity and claims were located in the vicinity of the gold panning area through the late 1880's and early 1890's, but no major mining development took place. On June 28, 1890, J.T. Vaughan and H.F. Greenwell located the Horseshoe Placer. They continued to locate and work other claims in the area of the gold panning area and surrounding claims until the early 1900's, when they patented and leased their claims. These miners were some of the initial developers of the present gold panning area. In 1899-1900, Vaughan and Greenwell hand dug a mining ditch from a point above Libby Creek Falls to their mining claims. This 6,000-foot-long ditch supplied water necessary for placer and subsequent hydraulic mining ventures.
The mineral claims in the gold panning area were surveyed in 1901 by Nimrod E. Jenkins and patented shortly thereafter. Vaughan and Greenwell began ground sluicing in the area of the present gold panning area in the early 1900's and later leased their claims from 1904 to 1908. The firm of Cannon and Lee of Spokane, Washinglon later bought claims in the area and established hydraulic mining operations in about 1909. One of the partners died, and the properties in the gold panning area were tied up in court for years.
In 1930, L.J. Olson and Harry Bolyard acquired the former Vaughan and Greenwell properties from a Mr. Curtiss. They sold the properties in 1931, and in 1932 the Libby Placer Mining Company began installation of hydraulic mining equipment and flumes on their mining claims on Howard and Libby Creek. There were 15 men employed lo work the operation. The cabins, seen near the bridge crossing over Libby Creek, were built in 1932 by the Libby Placer Mining Company. This operation was unsuccessful and the property was reacquired by Harry Bolyard and L.J. Olson of the Liberty Placer Mining Company. The Liberty Placer Mining Company resumed hydraulic mining operations in the old mining area of Vaughan and Greenwell from 1935 to 1937. After difficulties arose from disposal of tailings, both gasoline and dieseI-powered earthmoving shovels were used to excavate goldbearing gravels.
In April ol 1938, a dryland dredge worked the gold panning area. This dredge, in operation until April of 1940, processed gravels which were fed into it by the diesel-powered Bucyrus-Erie shovel,
Hydraulic operations on a small scale recommenced and were utilized in what is now the gold panning area until 1947. With the use of hydraulic hoses, bulldozers, and sluice boxes, 15,000 cubic yards of material were processed in 1947 and a value ol $6,600.00 in gold (1947 gold prices) was recovered from the mining area. Sporadic mining took place at the Liberty or Bolyard Placer until 1987 when the patented claims, which constitute the present gold panning area, were acquired through a land exchange. The gold panning area was established for the public in 1988 and withdrawn from mineral entry.
Though no one ever made a fortune on Libby Creek, wages were made there for decades. The creek continues to be prospected and placer mined to the present day.
Please do not collect or vandalize historic cabins, artifacts, or mining equipment so that we can all learn from the history of the area. Please do not disturb historic materials or equipment while excavating for gold.
Contact the Libby District Office for more information regarding gold panning.
Announcing the "NATURE in Our Own Backyard" photo contest.
Enter to win the Grand Prize of a 3-day fully guided canoe trip for two on the spectacular Wild and Scenic Missouri River. The Montana Office of Tourism has partnered with Montana PBS to give photographers an opportunity to showcase the best place ever to vacation - Montana! The theme this year encourages Montana families to use their vacation funds exploring all that Montana has to offer. The categories for submissions include: (1) general family vacation locations; (2) national or state park locations, (3) a series of six pictures that tell a Montana story. In addition to the grand prize, there will be a prize awarded for each of the three categories.
For contest details, go to www.montanapbs.org
Contest ends July 31, 2009.
I loved this video as it depicts the route of the historic Northern Pacific Railroad through this beautiful corner of northwestern Montana. I am sure you will enjoy the journey as much as I did.
Wild, clear, big and beautiful, the Kootenai River courses through heavily forested mountains, much of its path through still remote wilderness. It is a magnificent river, providing excellent fishing and incredible scenery as it twists and turns on its way to the Columbia. Eagles, hawks and osprey call the river home and deer, elk and mountain sheep abound.
The Kootenai River has its origins in British Columbia's Kootenay National Park north of Mt. Assiniboine, the highest point in the drainage at 11,867 ft. elevation. Commencing there, it flows 485 miles into northwest Montana near Eureka and through the towns of Libby and Troy. Sixteen miles north of Libby, the river is held back by Libby Dam, creating a 85-mile long reservoir called Lake Koocanusa which reaches into Canada.
Downstream from Libby, the river races through a small canyon and dances over Kootenai Falls. Kootenai Falls is one of the largest free-flowing waterfalls in the northwest; an area sacred site to the Kootenai Indians whose ancestors once lived along its bountiful banks.
From there, the majestic Kootenai travels into northern Idaho through the town of Bonners Ferry, then traverses back into Canada. The river re-enters Canada south of Creston, British Columbia and widens into Kootenay Lake. Near Nelson, British Columbia, the Kootenay becomes a river again and flows southwest towards Castlegar, British Columbia where it joins the Columbia River. The Kootenai is one of the very few rivers in North America which begins in Canada, enters the United States and then re-enters Canada. The Kootenay River (spelled Kootenai River for its American segments) is the uppermost major tributary of the Columbia River.
The Kootenai River is the second largest tributary to the Columbia River in terms of run-off volume, ranked third by the size of it’s drainage area. The major tributaries of the Kootenai River are the St. Mary, Slocan, Bull Elk, Fisher, Yaak and Moyie Rivers. The Kootenai Basin is largely mountainous and dominated by three major ranges. The Rocky Mountain Range and its offshoot, the Flathead Range, mark the eastern boundary; the Purcell Range roughly bisects it from north to south. The Selkirk and Cabinet ranges constitute the western boundary. Elevations reach a maximum of about 12,000 feet with most summit elevations between 6,000 and 7,500 feet. Except for a few low lying areas, the entire watershed is densely forested or above the tree line.
The Kootenai River was named in honor of the indigenous Kootenai people that inhabited the remote and pristine wilderness. Early history of the area shows that these proud people were also known as the Ktunaxa in Canada and were most often referred to as the Flatbows and the majestic river was called the Flatbow River.
The first white man to explore the area, David Thompson, an English-Canadian fur trapper, surveyor and map-maker traveled down the river in May of 1808 in an effort to establish a fur trading district in the Columbia River system. Thompson who was known to the native peoples as “Koo-Koo-Sint” or “the Stargazer” was enchanted with the river. In 1809 he named the river McGillivray’s River, in honor of Duncan and William McGillivray, partners in the Northwest Company that had financially supported David Thompson’s quests.
David Thompson (1770-1857) played a significant role in the history of the Kootenai River and the exploration of the American West. Described as the “greatest land geographer who ever lived”, David Thompson during his long career mapped over 3.9 million square kilometres of North America.
In 1863, gold was discovered at the confluence of the Kootenay and Wild Horse Rivers. The Wild Horse Gold Rush brought several thousand men into the area and resulted in the building of Fisherville, British Columbia which was later moved when it was discovered that the new mining townsite sat atop of some of the areas richest ore deposits.
The rush was short lived and by 1885 most of the men had moved on to other strikes. Gold rushes on the Moyie and Goat Rivers were rapidly followed by the discovery of galena and silver in the Kootenay Lake and Slocan Valley regions, leading to a rapid settlement of the area and the creation of mining boomtowns; Nelson, at the outlet of Kootenay Lake, Kaslo, mid-point up the northern arm and the majestic Lardo district at the northern end of Kootenay Lake. Mining motivated the fed the development of the upper Kootenay River between Cranbrook-Fort Steel and to points in Montana. Powerful steamboats such as the USS Moyie navigated the river from Bonners Ferry, Idaho into the northern towns of British Columbia, carrying miners and their supplies.
Famous for its world class fishing, the Kootenai River has a large population of cutthroat trout, bull trout, Kokanee salmon and rainbow trout. Impressive White Sturgeon are found in the river below Kootenai Falls. In 1972, the completion of Libby Dam brought marked change to the water ecosystem and created conditions in which several species of fish thrive. White sturgeon in the Kootenai River were recognized as endangered in 1994. In a valiant effort to protect and re-populate this awesome fish, the Kootenai Tribe of Idaho established the Kootenai Sturgeon Hatchery to implement an aquaculture recovery program. The recovery program protects the sturgeon population from possible extinction.
The Kootenai River and many of its tributaries are the only waters in Montana where anglers can find a native strain of rainbow trout known as the Columbia River Redbands. The Columbia River Redbands are only indigenous to the head-waters of the Columbia River which includes the Kootenai.
Do you have gold fever?
It is a magnificent, sun-blessed day here in Montana. The mountains are a deep, verdent green, lush with tall grasses and the burst of new growth amonst the pine, spruce and tamarack trees. There are still patches of snow in the high country, wild flowers in glorious profusion grace the sunny slopes; the rivers and creeks run full.
I have a dense woods on my property. I would love to have a "tree house" like this - what a great guest house or ideal way to live off the grid. Found this great article and wanted to share will all our readers!
The “Spherical Tree House” concept borrows heavily from sailboat construction and rigging practice. It’s a marriage of tree house and sailboat technology. Wooden spheres are built much like a cedar strip canoe or kayak. Suspension points are similar to the chain plate attachments on a sailboat. Stairways hang from a tree much like a sailboat shroud hangs from the mast.
Spherical architecture has many unconventional features. Conventional buildings separate walls, ceiling and floor with hard lines. In a sphere the walls and ceiling merge into one. The function changes but the form remains the same. It is a unified structure with one continuous wall. I call this uniwall construction. There are only 2 sides to a sphere, inside and outside.
In bio-mimicry fashion, the nut like shape attaches to a web of rope. The web connects to which ever strong points are available. This replaces the foundation of a conventional building. A tree house sphere uses the forest for its foundation. The occupants have a vested interest in the health of the grove. The supporting web also mirrors our connectedness to our eco-system. Each sphere has four attachments on top and another four anchor points on the boom. Each attachment is strong enough to carry the entire sphere and contents.
A suspended sphere is tethered by 3 nearly vertical ropes to each of 3 separate trees. This distributes the load evenly over the 3 trees and results in a stable hang. Like an inverted three-legged stool, there will be almost equal tension in each of the three suspension ropes. The sphere resides in the center of the triangle formed by the 3 trees. It can be slung from 5 to 100′ off the ground, depending on the size of the trees. The triangle formed by 3 old trees was called a sacred grove in the druids tradition. Each grove was influenced by the type and age of the trees. I’ve found that to be my experience as well. The flavour of a grove changes considerably with the type of trees.
A sphere is accessed by a spiral stairway and short suspension bridge. The two lower back suspension points of the sphere are tied horizontally to the two back trees, to keep the suspension bridge from sagging when it is walked on. The door faces the “door tree” and the suspension bridge connects the two. A helical stairway spirals up or down from the suspension bridge to the ground or next level.
Externally the spherical shape is well adapted to life in the forest. A hazard of life in the forest is trees and branches falling in a strong wind or ice storm. A sphere distributes any impact stress throughout the skin and resists puncture or cracking. Like a ping pong ball or a nut, it’s light with a tough skin. The suspension ropes which stretch also absorb some of the force.
The suspension concept is also bio-mimicry. The idea is to have the sphere and web function naturally in its environment. If something really big, like a tree, falls through the web then some strands will break and let it pass through. The sphere remains suspended by the remaining strands. A major disaster like that is not likely, but possible. Everything including spiral stairways and suspension bridges are hung from ropes. Trees are protected where the spiral stairways hug the trees and ropes pass around the trees. The spheres are well adapted to life in a large mature forest.
More detailed photos of the interior feature of both wooden and fiberglass spheres can be viewed at:
Gold is where you find it, but this is an unexpected place. I found this article while searching for mining information and wanted to share with everyone.
TOKYO (Reuters) - Resource-poor Japan just discovered a new source of mineral wealth -- sewage.
A sewage treatment facility in central Japan has recorded a higher gold yield from sludge than can be found at some of the world's best mines. An official in Nagano prefecture, northwest of Tokyo, said the high percentage of gold found at the Suwa facility was probably due to the large number of precision equipment manufacturers in the vicinity that use the yellow metal. The facility recently recorded finding 1,890 grammes of gold per tonne of ash from incinerated sludge.
That is a far higher gold content than Japan's Hishikari Mine, one of the world's top gold mines, owned by Sumitomo Metal Mining Co Ltd, which contains 20-40 grammes of the precious metal per tonne of ore.
The prefecture is so far due to receive 5 million yen ($55,810) for the gold, minus expenses.
It expects to earn about 15 million yen for the fiscal year to the end of March from the gold it has retrieved from the ashes of incinerated sludge.
"How much we actually receive will depend on gold prices at the time," the official said.
Some gold industry officials expect prices this year to top the all-time high above $1,030 per ounce set in 2008, on buying by investors worried about the deepening economic downturn. (Reporting by Miho Yoshikawa; Editing by Hugh Lawson)
I am fascinated by gold and it's history. In my research I ran across this article that provides some good general background information and wanted to share it with my readers.
If you haven't had an opportunity to personally visit the National Mining Hall of Fame and Museum in Leadville, Colorado, grab a cup of coffee, sit back and visit their site. It is quite interesting and has a wealth of mining knowledge and history.
Through the ages men and women have cherished gold, and 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."
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.
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 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.
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 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 volcanic and sedimentary rocks, formed from circulating ground waters 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.
Placer deposits represent concentrations of gold derived from lode deposits by erosion, disintegration or decomposition of the enclosing rock, and subsequent concentration by gravity.
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."
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 gem stones 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.