Here is some state specific information to get you started on your search for gold and other valuable minerals. A lot of the basic information is drawn from Principal Gold-Producing Districts of the United States by A. H. Koschmann and M. H. Bergendahl, 1968 USGS Professional Paper 610 at https://pubs.usgs.gov/pp/0610/report.pdf and then updated where possible.
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Most of the principal gold-producing districts are in the mountainous areas of the United States, where folding, faulting, and igneous intrusions have deformed the rocks. In contrast, many large base-metal deposits are found in the large relatively un-deformed areas of the Central and Eastern States, but gold is not even a byproduct of these ores. Large parts of the Western States, such as the Colorado Plateau, the Columbia Plateau, and much of Wyoming, have not been subjected to violent tectonic forces and consequently contain very few gold deposits. Most of the gold deposits in the United States are associated with and are perhaps genetically related to small batholiths, stocks, and satellitic intrusive bodies of quartz monzonitic composition that range in age from Jurassic to Tertiary. Some deposits, such as those in the Southeastern States, may be genetically related to granitic bodies that were intruded at the close of Paleozoic time, and a few deposits, as at Jerome, Ariz., are Precambrian in age.
Gold was discovered in Alabama in the early 1830s. Recorded production to 1939 was about 49,000 troy ounces of gold; however, probably an equal amount has been mined but not reported. Gold has been produced from seven districts in the Alabama Piedmont Province. More than 100 prospects and mines are known in these seven districts. Gold mining ceased in Alabama, except on an individual basis, during the late 1930s. Exploration of gold deposits in Alabama has been carried out intermittently during the past several years in the historic gold districts. In 2008, gold prices exceeded $1,000 per troy ounce, increasing interest in the historic gold districts of the state. Minerals in the Economy of Alabama, 2007
Alaska has yielded over 40,416,575 ounces from the first discovery in 1848 through 2010. A large portion of this total was mined from placers in the Yukon region and the Seward Peninsula. The important lode-mining area in the past was Southeastern Alaska, where mines in the Juneau and Chichagof districts produced more than 7 million ounces of gold through 1959. More recently large lode mines in Interior Alaska such as Ft. Knox and Pogo have replaced Southeastern Alaska as the main sources of lode gold. Gold Prospecting Research Material for Alaska
Arizona’s cumulative gold production exceeds 16 million ounces contributed from 219 metallic mineral districts. Twenty-six of those districts have produced more than 100,000 ounces and 46 have produced more than 10,000 ounces. Much of the past gold production has been a by-product of large scale copper mining. Arizona hosts a number of deposits with known potential to produce a few hundred thousand ounces or more. Arizona Gold Prospecting
California has produced more gold than any other State - more than 106 million ounces from 1848 through 1965. The well-known discovery in El Dorado County in 1848 sparked a series of gold rushes that indirectly led to colonization of the entire mountain West. The rich gold placers of California yielded phenomenal wealth in the early years, and as the placers were depleted, prospectors searched for and found the source of the placer gold - the high-grade gold-quartz veins of the Mother Lode and Grass Valley. Others explored the forbidding mountain ranges of southern California and found productive lodes in the Cove, Rand, and Stedman districts. Placer mining was rejuvenated in the early 1900's with the introduction of large bucket dredges. From the late 1930's onward, dredging operations were responsible for a major part of California's gold output. Prospecting Research Material for California
Colorado ranks second among the gold-producing States; its gold output through 1965 was about 40,776,000 ounces. The first publicized discovery of gold in Colorado was in 1858. The immediate rush to the Denver area resulted in important placer finds near Idaho Springs and Central City. Prospectors ranging far up the Arkansas River valley found gold placers near Leadville as early as 1859. Many rich gold lodes were quickly discovered, and Colorado soon became a major mining area. In the 1870's, important ore discoveries were made in the San Juan Mountains, the Sawatch Mountains, and in the Leadville-Breckenridge area. Gold ore was found in the important Cripple Creek district in 1891. https://pubs.usgs.gov/pp/0610/report.pdf
Georgia is credited with a total historical production of 871,000 ounces of gold from 1830 through 1959. Although a historically important gold producer, the state does not presently produce anything more than minor amounts of gold.
Idaho, which ranks ninth among the gold-producing States, is credited with producing 8,323,000 ounces of gold from 1863 through 1965. The earliest recorded discovery in Idaho was of placer gold along the Pend Oreille River in 1852. Rich placers were found soon afterward at Pierce City, Elk City, Orofino, Boise Basin, Florence, and Warren, and a brief period of feverish activity followed. By 1870, many of the richer placers were exhausted, and an intensive search for lode deposits resulted. Large-scale dredging rejuvenated the placers, though after 1900, most of Idaho's gold was produced from lode mines. https://pubs.usgs.gov/pp/0610/report.pdf
Placer gold was discovered at Great Falls in 1861. A number of mines were opened on gold-bearing quartz veins in Montgomery County. No gold production has been reported since 1951. Total production was about 6,000 ounces.
In Michigan the only significant gold output has come from the Ropes mine in Marquette County near Ishpeming. Total production was about 29,000 ounces. https://pubs.usgs.gov/pp/0610/report.pdf
Montana, which yielded a total of 17,752,000 ounces of gold from 1862 through 1965, is seventh among the gold-producing States. Gold was first discovered in 1852 in placers in Powell County, but the influx of prospectors did not begin until the discovery of rich placers in the Bannack district in 1862. Numerous placers were found in rapid succession, among them those of Alder Gulch, which were to become the most productive placers in the State. Placers, which contributed almost half of Montana's total gold, had their greatest output before 1870; nevertheless, dredging and hydraulic placer mining were conducted on a large scale until World War II. Development of lodes, hindered by lack of railroads in the early days, progressed rapidly in the 1880's and was accelerated greatly with the expansion of operations at Butte in the early 1900's. https://pubs.usgs.gov/pp/0610/report.pdf
Though Nevada is primarily a silver-mining State, it produced a total of about 27,475,000 ounces of gold from 1859 through 1965 and ranks fifth among the gold-producing States. Mining began in the early 1850's and the period 1859-79 was the boom era of the Comstock Lode and Reese River districts. After a period of decline from 1880 to 1900, the discoveries at Tonopah and Goldfield rejuvenated mining in the State until World War I. Lead, zinc, and copper mining, which yield gold as a byproduct, dominated Nevada's mining industry from the end of World War I through 1959, although for short periods large gold operations in the Potosi, Round Mountain, and Bullion districts have been significant. Discovery of the Carlin gold deposit in 1962 has revived interest in the gold potential of the State. https://pubs.usgs.gov/pp/0610/report.pdf
New Mexico produced about 2,267,000 ounces of gold from 1848 through 1965. Though gold lodes were worked on a small scale as early as 1833, prospectors showed little interest in the territory until the 1860's and 1870's. In rapid succession, lode and placer gold and rich silver and silver-lead discoveries were made, and mining flourished. By 1900, however, the oxidized ores were depleted, and interest turned to developing the primary base-metal ores from which gold is produced as a byproduct. This trend continued, in general, through 1959. The major gold districts are Elizabeth-town-Baldy, Mogollon, and Lordsburg. https://pubs.usgs.gov/pp/0610/report.pdf
North Carolina was the site of the first gold rush in the United States, following the discovery of a 17 pound gold nugget by 12-year old Conrad Reed in a creek at his father’s farm in 1799. North Carolina produced about 50,000 ounces of gold from lode and placer deposits.
Oregon, the tenth most important gold-mining State, produced 5,797,000 ounces of gold from 1852 through 1965. Gold placers were worked as early as 1852, but the great rush to Oregon did not take place until 1861, after the placer discovery at Griffin Gulch in Baker County. After an initial period of high placer output, gold lodes were found and developed at a less frenzied rate. By the early 1900's, gold mining began a decline that lasted until 1934 when it was rejuvenated by the increase in the price of gold. A few districts, notably the Sumpter, were then reactivated, and gold mining was revived through the late 1930's and early 1940's until the demands of World War II diverted mining to commodities other than gold. Gold mining in Oregon in the post-World War II period has been in a steady decline. https://pubs.usgs.gov/pp/0610/report.pdf
Most of Pennsylvania's gold has been produced from the Cornwall iron mine in Lebanon County.* Where to Find Gold in Pennsylvania and Gold in Pennsylvania. https://pubs.usgs.gov/pp/0610/report.pdf
Total gold production of South Carolina through 1959 was 318,801 ounces. High gold prices are leading to increased interest in South Carolina gold. Gold mining may commence soon at the historic Haile mine.
South Dakota, third among the gold-producing States, produced a total of about 31,208,000 ounces of gold through 1965, mostly from the Homestake mine. The gold districts are in the Black Hills in the northwestern part of the State. Most gold has been produced from lode deposits, but placers have also been mined. https://pubs.usgs.gov/pp/0610/report.pdf
Gold in Tennessee is a byproduct of the copper ores of the Ducktown district in Polk County; small amounts have been mined from placers on Coker Creek in Monroe County. Both areas are in the southeastern part of the State. Total production is over 14,000 ounces. https://pubs.usgs.gov/pp/0610/report.pdf
Utah, whose total gold output through 1965 was 17,765,000 ounces, ranks sixth among the gold-producing States. The first major ore discovery in the State was in 1863, when lead ore was found in Bingham Canyon. Gold placers were found nearby the following year. Silver-lead ore discoveries in the Cottonwood, Park City, and Tintic districts in the late 1860's and 1870's generated feverish activity which lasted until 1893 when the financial recession caused a sharp drop in the price of silver. In the early 1900's, large-scale mining of the low-grade copper ores of the Bingham district began. Gold has been an important byproduct of these ores. In 1965, the Bingham district, in addition to being one of the major copper producers of the world, was the second largest gold producer in the United States. The Tintic, Park City, and Camp Floyd districts also have yielded substantial amounts of gold. https://pubs.usgs.gov/pp/0610/report.pdf
About 100,000 troy ounces of gold were produced in Virginia from 1804 through 1947, when gold was last produced in the State. Gold in Virginia, 2007
Washington, whose total gold output from 1860 through 1965 was about 3,671,000 ounces, is one of the few States in which gold production has increased in recent years, mainly because of the output of the Knob Hill mine in the Republic district and the Gold King mine in the Wenatchee district. Gold was first discovered in the State in 1853 in the Yakima River valley. Placers were worked along most of the major streams of the State through the 1880's, but most of them were depleted by the early 1900's. Lode deposits were found in the 1870's and eventually supplanted placers as the chief source of gold. Of the 15 major gold districts of Washington, the most productive have been Republic, Wenatchee, and Chelan Lake. https://pubs.usgs.gov/pp/0610/report.pdf
Wyoming is a minor gold-producing State; its total output through 1965 was over 180,000 ounces. Only two districts - the Douglas Creek and the Atlantic City-South Pass - have been significant. https://pubs.usgs.gov/pp/0610/report.pdf
Nobody knows what the production figures are but there is little doubt hundreds of thousands of ounces of gold have been found in Australia by prospectors with metal detectors in the last 40 years. Gold in Australia