Gold prospecting
Encyclopedia
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
deposits. Methods used vary with the type of deposit sought and the resources of the prospector. Although traditionally a commercial activity, in some developed countries placer
Placer mining
Placer mining is the mining of alluvial deposits for minerals. This may be done by open-pit or by various surface excavating equipment or tunneling equipment....
gold prospecting has also become a popular outdoor recreation.
Prospecting for placer gold
Prospecting for placer gold is traditionally done with a gold pan or similar instrument to wash free gold particles from loose surface sediment. The use of gold pans is centuries old, but is still common among prospectors and miners with little financial backing.Deeper placer deposits may be sampled by trenching or drilling. Geophysical methods such as seismic, gravity or magnetics may be used to locate buried river channels that are likely locations for placer gold. Sampling and assaying a placer gold deposit to determine its economic viability is subject to many pitfalls.
Once placer gold is discovered, the gold pan is usually replaced by sluices or mechanical devices to wash greater volumes of material. Discovery of placer gold has often resulted in discovery of hardrock gold deposits when the placers are traced to their sources.
Prospecting for hardrock gold deposits
Prospectors for hardrock, or lodeLode
In geology, a lode is a deposit of metalliferous ore that fills or is embedded in a fissure in a rock formation or a vein of ore that is deposited or embedded between layers of rock....
gold deposits, can use many tools. It is done at the simplest level by surface examination of rock outcrops, looking for exposures of mineral veins
Vein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation...
, hydrothermal
Hydrothermal circulation
Hydrothermal circulation in its most general sense is the circulation of hot water; 'hydros' in the Greek meaning water and 'thermos' meaning heat. Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust...
alteration, or rock types known to host gold deposits. Field tools may be nothing more than a rock hammer and hand lens.
Hardrock gold deposits are more varied in mineralogy
Mineralogy
Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...
and geology than placer deposits, and prospecting methods can be very different for different types of deposits. As with placer gold, the sophistication of methods used to prospect for hardrock gold vary with the financial resources of the prospector. Drilling is often used to explore the subsurface. Surface geophysical
Geophysics
Geophysics is the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and...
methods may be used to locate geophysical anomalies associated with gold deposits. Samples of rocks or soil may be collected for geochemical
Geochemistry
The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks, water, and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and...
laboratory assay, to determine metal content or detect geochemical anomalies. Hardrock gold particles may be too small to see, even with a microscope.
Most gold today is produced in large open-pit
Open-pit mining
Open-pit mining or opencast mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow....
and deep underground mines. However, small-scale gold mining is still common, especially in third-world countries.
Recreational prospecting
Small-scale recreational prospecting for placer gold has been seen in many parts of the world including New ZealandNew Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
(especially in Otago), Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
(at Dolaucothi
Dolaucothi Gold Mines
The Dolaucothi Gold Mines , also known as the Ogofau Gold Mine, are Roman surface and deep mines located in the valley of the River Cothi, near Pumsaint, Carmarthenshire, Wales...
and in Gwynedd
Gwynedd
Gwynedd is a county in north-west Wales, named after the old Kingdom of Gwynedd. Although the second biggest in terms of geographical area, it is also one of the most sparsely populated...
), in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
especially in western states but also elsewhere.
See also
- Gold mining in AlaskaGold mining in AlaskaGold mining in Alaska, a state of the United States, has been a major industry and impetus for exploration and settlement since a few years after the United States acquired the territory from Russia. Russian explorers discovered placer gold in the Kenai River in 1848, but no gold was produced...
- Gold in CaliforniaGold in CaliforniaGold in California became highly concentrated there as the result of global forces operating over hundreds of millions of years. Volcanoes, tectonic plates and erosion all combined to concentrate billions of dollars worth of gold in the mountains of California...
- Gold nuggetGold nuggetA gold nugget is a naturally occurring piece of native gold. Watercourses often concentrate and grow the nuggets. Nuggets are recovered by placer mining, but they are also found in residual deposits where the gold-bearing veins or lodes are weathered...
- Gold panningGold panningGold panning, or simply panning, is a form of placer mining that extracts gold from a placer deposit using a pan. The process is one of the simplest ways to extract gold, and is popular with geology enthusiasts because of its cheap cost and the relatively simple and easy process involved. It is the...
- Gold Prospectors Association of AmericaGold Prospectors Association of AmericaThe Gold Prospectors Association of America is an organization dedicated to finding and mining gold on a small or recreational scale. It has gold claims across America and members can work the claims for a yearly fee. The club is headquartered in Temecula, California. Most, if not all GPAA...
- Gold rushGold rushA gold rush is a period of feverish migration of workers to an area that has had a dramatic discovery of gold. Major gold rushes took place in the 19th century in Australia, Brazil, Canada, South Africa, and the United States, while smaller gold rushes took place elsewhere.In the 19th and early...
- HushingHushingHushing is an ancient and historic mining method using a flood or torrent of water to reveal mineral veins. The method was applied in several ways, both in prospecting for ores, and for their exploitation. Mineral veins are often hidden below soil and sub-soil, which must be stripped away to...
- Mineral explorationMineral explorationMineral exploration is the process of finding ore to mine. Mineral exploration is a much more intensive, organized and professional form of mineral prospecting and, though it frequently uses the services of prospecting, the process of mineral exploration on the whole is much more involved.-Stages...
- Placer miningPlacer miningPlacer mining is the mining of alluvial deposits for minerals. This may be done by open-pit or by various surface excavating equipment or tunneling equipment....
- Recreational gold miningRecreational gold miningRecreational gold mining and prospecting has become a popular outdoor recreation in a number of countries, including New Zealand , Australia, South Africa, Wales , in Canada and in the United States especially in western states but also elsewhere...
External links
- USGS article on gold prospecting
- Public Gold Fossicking Areas in New Zealand
- Modern-Day Gold Diggers - slideshow by NPRNPRNPR, formerly National Public Radio, is a privately and publicly funded non-profit membership media organization that serves as a national syndicator to a network of 900 public radio stations in the United States. NPR was created in 1970, following congressional passage of the Public Broadcasting...