Gold Deposit
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Gold may occur as deposits called lodes, or veins, in fractured rock. It may also be dispersed within Earth's crust. Most lode deposits form when heated fluids circulate through gold-bearing rocks, picking up gold and concentrating it in new locations in the crust.
- World's Largest Deposits of Gold The massive deposits of the Witwatersrand mines in South Africa have produced more than 40 percent of the world's total production of gold. The origin of these ancient ores-several billion years old-is controversial.
- New Theory Suggests Gold Deposits Were Formed as a Result of Earthquakes A new theory based on a simple but viable geologic model claims that over 80 percent of all commercial gold deposits were formed in a flash. Bounty Hunter Metal Detector.
- Gold deposit - Find potential answers to this crossword clue at crosswordnexus.com.
- Resident Indians can deposit gold under Gold Monetisation Scheme. The deposit will be denominated in grams of gold with purity 995. The deposit will help the depositor earn interest at the rate of interest decided by Central Government and notified by Reserve Bank of India from time to time.
Republished from 'Prospecting for Gold in the United States,'
a general interest publication of the US Geological Survey by Harold Kirkemo.
Lode gold: Gold ore from the Olinghouse epithermal deposit. When gold is found in the rocks where it crystallized, it is known as a 'lode deposit.' USGS image.
The Many Rewards of Finding Gold
Anyone who pans for gold hopes to be rewarded by the glitter of colors in the fine material collected in the bottom of the pan. Although the exercise and outdoor activity experienced in prospecting are rewarding, there are few thrills comparable to finding gold. Even an assay report showing an appreciable content of gold in a sample obtained from a lode deposit is exciting. The would-be prospector hoping for financial gain, however, should carefully consider all the pertinent facts before deciding on a prospecting venture.
Few Prospectors Find Valuable Gold Deposits
Only a few prospectors among the many thousands who searched the western part of the United States ever found a valuable deposit. Most of the gold mining districts in the West were located by pioneers, many of whom were experienced gold miners from the southern Appalachian region, but even in colonial times only a small proportion of the gold seekers were successful.
Hydrogeochemical prospecting for gold: Groundwater collected from wells, springs, and drill holes may provide clues to the presence of subsurface gold deposits. As groundwater flows through the deposit, minute amounts of gold are leached from the rocks. These can sometimes be detected in groundwater samples collected from wells located down gradient from the deposit. USGS image.
The US Has Been Heavily Prospected
Over the past several centuries the country has been thoroughly searched by prospectors. During the depression of the 1930's, prospectors searched the better known gold-producing areas throughout the Nation, especially in the West, and the little-known areas as well. The results of their activities have never been fully documented, but incomplete records indicate that an extremely small percentage of the total number of active prospectors supported themselves by gold mining. Of the few significant discoveries reported, nearly all were made by prospectors of long experience who were familiar with the regions in which they were working.
Gold Panning made easy: Gary Smith, a gold panner from British Colombia with 40 years of experience, demonstrates his panning methods and gives advice. More gold panning videos.
Prospect Where Gold Has Been Found Before
The lack of outstanding success in spite of the great increase in prospecting during the depression in the 1930's confirms the opinion of those most familiar with the occurrence of gold and the development of gold mining districts that the best chances of success lie in systematic studies of known productive areas rather than in efforts to discover gold in hitherto unproductive areas.
The development of new, highly sensitive, and relatively inexpensive methods of detecting gold, however, has greatly increased the possibility of discovering gold deposits which are too low grade to have been recognized earlier by the prospector using only a gold pan. These may be large enough to be exploited by modern mining and metallurgical techniques. The Carlin mine near Carlin, Nevada, produced gold from a large low-grade deposit that was opened in 1965 after intensive scientific and technical work had been completed. Similar investigations have led to the discovery of a Carlin-type gold deposit in Jerritt Canyon, Nevada.
Gold Panning made easy: Gary Smith, a gold panner from British Colombia with 40 years of experience, demonstrates his panning methods and gives advice. More gold panning videos.
Gold dredge: A floating gold dredge operating near Fairplay, Colorado in 1950. Machines like this could dredge up hundreds of tons of sediment per day and process it to remove the gold. USGS image.
Many Placer Deposits Have Been Worked - Twice
Many believe that it is possible to make wages or better by panning gold in the streams of the West, particularly in regions where placer mining formerly flourished. However, most placer deposits have been thoroughly reworked at least twice--first by Chinese laborers, who arrived soon after the initial boom periods and recovered gold from the lower grade deposits and tailings left by the first miners, and later by itinerant miners during the 1930's.
Geologists and engineers who systematically investigate remote parts of the country find small placer diggings and old prospect pits whose number and wide distribution imply few, if any, recognizable surface indications of metal-bearing deposits were overlooked by the earlier miners and prospectors.
Convergent plate boundaries are the plate tectonic setting of many gold deposits. There, magma produced by the melting of descending lithosphere rises as magma chambers and crystallizes close to the surface. Gold in these hot environments is often dissolved in superheated water and carried away from the magma chamber along faults and fractures. The water temperature is very high near the magma chamber but drops with distance. As the water travels farther from the magma chamber, gold starts to crystallize out within the fracture to produce a vein gold deposit. USGS image.
Financial Challenges of Gold Prospecting
One who contemplates prospecting for gold should realize that a successful venture does not necessarily mean large profits even if the discovery is developed into a producing mine. Although the price of gold has increased significantly since 1967 when the fixed price of $35 an ounce was terminated, the increases in the cost of virtually every supply and service item needed in prospecting and mining ventures have kept profit margins at moderate levels, particularly for the small mine operator. In general, wide fluctuations in the price of gold are not uncommon, whereas inflationary pressures are more persistent. The producer of gold, therefore, faces uncertain economic problems and should be aware of their effects on his operation.
Convergent boundary map: A present-day convergent boundary is located along the Pacific Northwest portion of the United States and extends north along the coast of Canada. Volcanic activity there will produce the gold deposits of the future. Gold deposits being mined today were produced by ancient activity on current plate boundaries or ancient activity on boundaries that are no longer active. USGS image.
Knowledge of Laws and Property Ownership
Today's prospector must determine where prospecting is permitted and be aware of the regulations under which he is allowed to search for gold and other metals. Permission to enter upon privately owned land must be obtained from the land owner. Determination of land ownership and location and contact with the owner can be a time-consuming chore but one which has to be done before prospecting can begin.
Determination of the location and extent of public lands open to mineral entry for prospecting and mining purposes also is a time consuming but necessary requirement. National parks, for example, are closed to prospecting. Certain lands under the jurisdiction of the Forest Service and the Bureau of Land Management may be entered for prospecting, but sets of rules and regulations govern entry. The following statement from a pamphlet issued in 1978 by the U.S. Department of the Interior and entitled 'Staking a mining claim on Federal Lands' responds to the question 'Where May I Prospect?'
'There are still areas where you may prospect, and if a discovery of a valuable, locatable mineral is made, you may stake a claim. These areas are mainly in Alaska, Arizona, Arkansas, California, Colorado, Florida, Idaho, Louisiana, Mississippi, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Utah, Washington, and Wyoming. Such areas are mainly unreserved, unappropriated Federal public lands administered by the Bureau of Land Management (BLM) of the U.S. Department of the Interior and in national forests administered by the Forest Service of the U.S. Department of Agriculture. Public land records in the proper BLM State Office will show you which lands are closed to mineral entry under the mining laws. These offices keep up-to-date land status plats that are available to the public for inspection. BLM is publishing a series of surface and mineral ownership maps that depict the general ownership pattern of public lands. These maps may be purchased at most BLM Offices. For a specific tract of land, it is advisable to check the official land records at the proper BLM State Office.'
Core drilling for gold: Core drilling the Bend massive sulfide deposit, located in the Medford District of the Chequamegon National Forest, Michigan. It is a small, metal-rich sulfide body hosted by Early Proterozoic Penokean volcanics. The mineralized horizon subcrops beneath 100-120 feet of glacial cover, and consists of massive pyrite with varying amounts of chalcopyrite, tetrahedrite-tenantite, bornite, arsenopyrite, chalcocite, and rare gold-silver tellurides. USGS image.
Small Prospectors and Total Gold Production
Successful gold mining under present conditions is a large-scale operation, utilizing costly and sophisticated machinery capable of handling many tons of low-grade ore each day. The grizzled prospector with a burro is no longer a significant participant in the search for mineral deposits, and the small producer accounts for only a minor share of the total production of metals including gold.
Gold core at the lab: The core recovered from the Bend massive sulfide deposit (see drilling photo above) was 3' in diameter and was recovered in 10-foot sections. The sections were extracted from the drill stem into plastic bags and taken to a laboratory for careful examination, sampling and analysis. USGS image.
Study, Persistence and Financial Backing
Some degree of success in finding gold still remains for those choosing favorable areas after a careful study of mining records and the geology of the mining districts. Serious prospecting should not be attempted by anyone without sufficient capital to support a long and possibly discouraging campaign of preliminary work. The prospective gold seeker must have ample funds to travel to and from the region he selects to prospect and to support the venture. He must be prepared to undergo physical hardships, possess a car capable of traveling the roughest and steepest roads, and not be discouraged by repeated disappointments. Even if a discovery of value is not found, the venture will have been interesting and challenging.
Fortitude Mine in Nevada produced about 2 million ounces of gold between 1984 and 1993. USGS image.
Public Information for Gold Prospectors
Locations of important gold-producing districts of the United States are shown in some of the reports of the United States Geological Survey listed at the bottom of this page. Geological surveys of the principal gold-producing States where additional information may be obtained also are listed. Information may be obtained, too, from U.S. Bureau of Mines State Liaison offices located in the capital cities of most States. There are also a large number of layman's books about gold that describe gold deposits and gold prospecting.
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 Geology of Placer Deposits
A placer deposit is a concentration of a natural material that has accumulated in unconsolidated sediments of a stream bed, beach, or residual deposit. Gold derived by weathering or other process from lode deposits is likely to accumulate in placer deposits because of its weight and resistance to corrosion. In addition, its characteristically sun-yellow color makes it easily and quickly recognizable even in very small quantities. The gold pan or miner's pan is a shallow sheet-iron vessel with sloping sides and flat bottom used to wash gold-bearing gravel or other material containing heavy minerals. The process of washing material in a pan, referred to as 'panning,' is the simplest and most commonly used and least expensive method for a prospector to separate gold from the silt, sand, and gravel of the stream deposits. It is a tedious, back-breaking job and only with practice does one become proficient in the operation.
California Placer Deposits
Many placer districts in California have been mined on a large scale as recently as the mid-1950's. Streams draining the rich Mother Lode region--the Feather, Mokelumne, American, Cosumnes, Calaveras, and Yuba Rivers--and the Trinity River in northern California have concentrated considerable quantities of gold in gravels. In addition, placers associated with gravels that are stream remnants from an older erosion cycle occur in the same general area.
Alaska Placer Deposits
Much of the gold produced in Alaska was mined from placers. These deposits are widespread, occurring along many of the major rivers and their tributaries. Some ocean beach sands also have been productive. The principal placer-mining region has been the Yukon River basin which crosses central Alaska. Dredging operations in the Fairbanks district have been the most productive in the State. Beach deposits in the Nome district in the south-central part of the Seward Peninsula rank second among productive placer deposits of Alaska. Other highly productive placers have been found in the drainage basin of the Copper River and of the Kuskokwim River.
Montana Placer Deposits
In Montana, the principal placer-mining districts are in the southwestern part of the State. The most productive placer deposit in the State was at Alder Gulch near Virginia City in Madison County. Other important placer localities are on the Missouri River in the Helena mining district. The famous Last Chance Gulch is the site of the city of Helena. There are many districts farther south on the headwaters and tributaries of the Missouri River, especially in Madison County which ranks third in total gold production in the State. Gold has been produced at many places on the headwaters of the Clark Fork of the Columbia River, particularly in the vicinity of Butte. Placer production from the Butte district, however, has been over-shadowed by the total output of byproduct gold recovered from the mining of lode deposits of copper, lead, and zinc.
Idaho Placer Deposits
Idaho was once a leading placer-mining State. One of the chief dredging areas is in the Boise Basin, a few miles northeast of Boise, in the west-central part of the State. Other placer deposits are located along the Salmon River and on the Clearwater River and its tributaries, particularly at Elk City, Pierce, and Orofino. Extremely fine-grained (or 'flour') gold occurs in sand deposits along the Snake River in southern Idaho.
Colorado Placer Deposits
Placers in Colorado have been mined in the Fairplay district in Park County, and in the Breckenridge district in Summit County. In both areas large dredges were used during the peak activity in the 1930's.
Oregon Placer Deposits
The most important mining regions of Oregon are in the northeastern part of the State where both lode and placer gold have been found. Placer gold occurs in many streams that drain the Blue and Wallowa Mountains. One of the most productive placer districts in this area is in the vicinity of Sumpter, on the upper Powder River. The Burnt River and its tributaries have yielded gold. Farther to the west, placer mining (particularly dredging) has been carried on for many years in the John Day River valley. In southwestern Oregon, tributaries of the Rogue River and neighboring streams in the Klamath Mountains have been sources of placer gold. Among the main producing districts in this region are the Greenback district in Josephine County and the Applegate district in Jackson County.
South Dakota and Washington
Minor amounts of placer gold have been produced in South Dakota (the Black Hills region, particularly in the Deadwood area, and on French Creek, near Custer) and in Washington (on the Columbia and Snake Rivers and their tributaries).
Nevada, Arizona, New Mexico
In addition to these localities, placer gold occurs along many of the intermittent and ephemeral streams of arid regions in Nevada, Arizona, New Mexico, and southern California. In many of these places a large reserve of low-grade placer gold may exist, but the lack of a permanent water supply for conventional placer mining operations requires the use of expensive dry or semidry concentrating methods to recover the gold.
Eastern US Placer Deposits
In the eastern States, limited amounts of gold have been washed from some streams draining the eastern slope of the southern Appalachian region in Maryland, Virginia, North Carolina, South Carolina, Georgia, and Alabama. Many saprolite (disintegrated somewhat decomposed rock that lies in its original place) deposits in this general region also have been mined by placer methods. Small quantities of gold have been mined by placer methods in some New England States. Additional placer deposits may be discovered in the East, but prospecting will require substantial expenditures of time and money. The deposits probably will be low grade, difficult to recognize, and costly to explore and sample. Moreover, most of the land in the East is privately owned, and prospecting can be done only with the prior permission and agreement of the land owner.
Gold Books and Panning Supplies
Looking for gold? We have over 50 different gold books and gold maps that show where gold has been found in the past and provide instruction on gold prospecting methods. Also available are gold pans in a variety of sizes and gold panning kits which include everything that you will need. Lode Gold
Lode gold occurs within the solid rock in which it was deposited. Areas likely to contain valuable lode deposits of gold have been explored so thoroughly that the inexperienced prospector without ample capital has little chance of discovering a new lode worth developing. Most future discoveries of workable lode gold ore probably will result from continued investigations in areas known to be productive in the past. The districts in which such new discoveries of gold may be possible are too numerous to be listed in detail in this pamphlet. Some of the famous districts are: in California, the Alleghany, Sierra City, Grass Valley, and Nevada City districts, and the Mother Lode belt; in Colorado, the Cripple Creek, Telluride, Silverton, and Ouray districts; in Nevada, the Goldfield, Tonopah, and Comstock districts; in South Dakota, the Lead district in the Black Hills; and in Alaska, the Juneau and Fairbanks districts. Deposits in these districts generally are gold-quartz lodes.
| Sources of Gold Information |
| There are many publications of interest to those seeking more information about gold. The United States Geological Survey has published lots of reports about general geology and mineral resources for most of the major gold-producing areas. In addition most state geological surveys where gold production has occurred have compiled reports and maps to document the general geology, deposits and mining activity. There are also lots of prospecting guides and maps geared to amateur prospectors. |
Lode Gold Areas Have Been Thoroughly Prospected
Prospecting for lode deposits of gold is not the relatively simple task it once was because most outcrops or exposures of mineralized rock have been examined and sampled. Today's prospector must examine not only these exposures, but also broken rock on mine dumps and exposures of mineralized rock in accessible mine workings.
Undiscovered Gold is Finely Disseminated
Gold, if present, may not be visible in the rock, and detection will depend on the results of laboratory analyses. Usually, samples of 3 to 5 pounds of representative mineralized rock will be sent to a commercial analytical laboratory or assay office for assay. Obviously, knowledge about the geological nature of gold deposits and particularly of the rocks and deposits in the area of interest will aid the prospector.
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Epithermal gold deposits are among the richest gold deposits in the world with some bonanza grade ore shoots containing more than 1000 g/t gold, or in other words, a kilogram of gold for every tonne of rock mined. Unfortunately, the tonnage of ore in epithermal veins is typically small compared with other types of lower grade gold deposits.
Gold mineralization within epithermal veins can occur over vertical intervals of a few hundred metres, vein thicknesses of 1-2 metres and lengths of up to several hundred metres. Epithermal deposits are typically high grade, small tonnage and relatively shallow deposits. They are best mined by underground narrow vein methods.
There are two main types of epithermal gold deposits; low and high sulphidation.
Low Sulphide Deposits
When ground water comes into contact with hot molten rock deep under volcanoes, silicate minerals within the rock are dissolved along with metals including gold, silver, arsenic, cadmium, lead, zinc, antimony and mercury. Large kilometre-scale circulation cells are set up by the movement of these heated ground waters, which are also known as hydrothermal fluids. These fluids move through cracks, joints and faults in the rock. As the fluids rise towards the surface, they cool with the precipitation of mainly quartz, some calcite and adularia, which is a type of potassium feldspar. Within the quartz veins are found concentrations of the metals being carried in the super-heated ground water.
Gold Deposits In Africa
High Sulphide DepositS
As the name suggests, high sulphide deposits tend to be more sulphide-rich; containing pyrite (iron sulphide), enargite (copper-arsenic sulphide) as well as gold and silver. They appear to be genetically and spatially linked to deep seated porphyry copper-gold deposits High sulphide deposits are formed in a similar manner to low sulphide deposits, just at a greater depth with a more direct link to the underlying magma.
Historically epithermal gold has been mined by underground techniques as miners followed the narrow, twisting veins from the surface outcrops far underground. Modern mining techniques, mean that today most epithermal deposits are mined using open-cut pit techniques.
The Toodoggone River camp and Queen Charlotte Islands provide excellent examples of Epithermal gold deposits.
Queen Charlottes Gold Rush, 1850
Gold Deposits Texas
Gold was first formally discovered by non-indigenous people at Gold Harbour on the west coast of MoresbyIsland in the Queen Charlotte Islands, near the Haida village of Tasu on Mitchell Inlet, an arm of Gold Harbour. A brief gold rush – the Queen Charlotte Gold Rush – ensued in the following year, leading to the declaration of the Colony of the Queen Charlotte Islands to prevent the archipelago from being overrun by Americans and so claimed by the United States.
The extent of the ore body proved superficial, and there are various stories of American prospecting parties harassed by the Haida people, who were still very numerous and powerful. In later times, Gold Harbour and Mitchell Inlet became the location of a modern mining operation, also called Tasoo or Tasu, but for iron rather than gold.
Gold Deposits
In 1969, a local logger, Efrem Specogna and his brother-in-law, John Trinco made the initial gold discovery of the Specogna (Babe) Gold deposit west of Port Clemens on Graham Island. By 1979, a 2 million ounce gold deposit was defined by exploratory drilling by major mining companies, Cominco, Kennco Explorations (a subsidiary of Kennecott) and Quintana Minerals. A junior exploration company continued drilling the project and a gold rush ensued from 1979-1981. The Specogna gold deposit remains an un-mined deposit with over 3 million ounces of gold and is categorized as an Epithermal type gold deposit.