Gossan ( eiserner hut or eisenhut ) is intensely oxidized , weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein . In the classic gossan or iron cap all that remains is iron oxides and quartz , often in the form of boxworks (which are quartz-lined cavities retaining the shape of the dissolved ore minerals). In other cases, quartz and iron oxides, limonite , goethite , and jarosite , exist as pseudomorphs, replacing the pyrite and primary ore minerals. Frequently, gossan appears as a red "stain" against the background rock and soil, due to the abundance of oxidized iron; the gossan may be a topographic positive area due to the abundance of erosion -resistant quartz and iron oxides. Although most gossans are red, orange, or yellow, black gossans from manganese oxides such as pyrolusite , manganite , and especially psilomelane form at the oxidized portion of manganese-rich mineral deposits.
14-496: In the 19th and 20th centuries, gossans were important guides to buried ore deposits used by prospectors in their quest for metal ores. An experienced prospector could read the clues in the structure of the gossans to determine the type of mineralization likely to be found below the iron cap . The name gossan appears to come from Cornish miner's slang. The terms "iron cap" and "iron hat", common in America, are direct translations from
28-421: A mining claim. The traditional methods of prospecting involved combing through the countryside, often through creek beds and along ridgelines and hilltops, often on hands and knees looking for signs of mineralization in the outcrop. In the case of gold, all streams in an area would be panned at the appropriate trap sites looking for a show of 'colour' or gold in the river trail. Once a small occurrence or show
42-404: A triangular head, with a very sharp point. The introduction of modern gravity and magnetic surveying methods has greatly facilitated the prospecting process. Airborne gravimeters and magnetometers can collect data from vast areas and highlight anomalous geologic features. Three-dimensional inversions of audio-magnetotellurics (AMT) is used to find conductive materials up to a few kilometers into
56-614: Is used for a variety of prospecting, but can mainly be for finding conductive materials. So far these low frequency EM techniques have been proven for geothermal exploration as well as for coal bed methane analysis. Geochemical prospecting involves analyzing the chemical properties of rock samples, drainage sediments, soils, surface and ground waters, mineral separates, atmospheric gases and particulates, and even plants and animals. Properties such as trace element abundances are analyzed systematically to locate anomalies. Geological mapping Too Many Requests If you report this error to
70-463: The 19th and early 20th century, it was very unlikely that a prospector would retire rich even if he was the one who found the greatest of lodes. For instance Patrick (Paddy) Hannan , who discovered the Golden Mile, Kalgoorlie , died without receiving anywhere near a fraction of the value of the gold contained in the lodes. The same story repeated at Bendigo, Ballarat, Klondike and California . In
84-491: The Earth, which has been helpful to locate kimberlite pipes, as well as tungsten and copper. Another relatively new prospecting technique is using low frequency electromagnetic (EM) waves for 'sounding' into the Earth's crust. These low frequency waves will respond differently based on the material they pass through, allowing for analysts to create three-dimensional images of potential ore bodies or volcanic intrusions. This technique
98-608: The German " Eiserner Hut " or " Eisenhut ", which term was also used in America. This rock -related article is a stub . You can help Misplaced Pages by expanding it . Prospectors Prospecting is the first stage of the geological analysis (followed by exploration ) of a territory. It is the search for minerals , fossils , precious metals, or mineral specimens. It is also known as fossicking . Traditionally prospecting relied on direct observation of mineralization in rock outcrops or in sediments. Modern prospecting also includes
112-619: The United States and Canada, prospectors were lured by the promise of gold , silver , and other precious metals . They traveled across the mountains of the American West , carrying picks, shovels and gold pans . The majority of early prospectors had no training and relied mainly on luck to discover deposits. Other gold rushes occurred in Papua New Guinea, Australia at least four times, Fiji, South Africa and South America. In all cases,
126-462: The gold rush was sparked by idle prospecting for gold and minerals which, when the prospector was successful, generated 'gold fever' and saw a wave of prospectors comb the countryside. Modern prospectors today rely on training, the study of geology, and prospecting technology. Knowledge of previous prospecting in an area helps in determining location of new prospective areas. Prospecting includes geological mapping , rock assay analysis, and sometimes
140-435: The intuition of the prospector. Prospecting of minerals found in mobile fluids, as is often the case of lithium , adds a "temporal element" to be considered. Metal detectors are invaluable for gold prospectors, as they are quite effective at detecting gold nuggets within the soil down to around 1 metre (3 feet), depending on the acuity of the operator's hearing and skill. Magnetic separators may be useful in separating
154-464: The magnetic fraction of a heavy mineral sand from the nonmagnetic fraction, which may assist in the panning or sieving of gold from the soil or stream. Prospecting pickaxes are used to scrape at rocks and minerals , obtaining small samples that can be tested for trace amounts of ore . Modern prospecting pickaxes are also sometimes equipped with magnets , to aid in the gathering of ferromagnetic ores. Prospecting pickaxes are usually equipped with
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#1732863355696168-432: The prospector to move onwards to the next and hopefully bigger and better show. Occasionally, the prospector would strike it rich and be joined by other prospectors to develop a larger-scale mining operation. Although these are thought of as "old" prospecting methods, these techniques are still used today, but usually coupled with more advanced techniques such as geophysical magnetic or gravity surveys. In most countries in
182-553: The use of geologic, geophysical , and geochemical tools to search for anomalies which can narrow the search area. Once an anomaly has been identified and interpreted to be a potential prospect direct observation can then be focused on this area. In some areas a prospector must also stake a claim, meaning they must erect posts with the appropriate placards on all four corners of a desired land they wish to prospect and register this claim before they may take samples. In other areas publicly held lands are open to prospecting without staking
196-489: Was found, it was then necessary to intensively work the area with pick and shovel, and often via the addition of some simple machinery such as a sluice box, races and winnows, to work the loose soil and rock looking for the appropriate materials (in this case, gold). For most base metal shows, the rock would have been mined by hand and crushed on site, the ore separated from the gangue by hand. These shows were commonly short-lived, exhausted and abandoned quite soon, requiring
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