Copper is a relatively abundant resource in the U.S., with over 1.15 million metric tons mined in 2012. It is used mainly for industrial uses, with approximately 45% being used in construction, and 23% used in electrical components. The vast majority of copper that is mined occurs in trace amounts within other minerals, averaging only 0.6% of the total composition of the ore. These ores generally have no added value as mineral specimens, and are processed strictly for the copper and other byproducts within the ore.
In a few locations throughout the U.S., copper is found in the form of natural nuggets and specimens occur, and are frequently found by prospectors using metal detectors to search for gold nuggets and other metallic objects. Natural copper nuggets and specimens can potentially occur in any area that has high amounts of copper, but the states of Arizona and Michigan are best known for producing copper nuggets and specimens.
In Arizona, copper nuggets are a fairly common occurrence in certain areas, and are often found by prospectors searching for gold nuggets and meteorites with metal detectors. Since copper is a non-ferrous metal, it can sound very similar to a gold nugget, so prospectors will dig them up along with gold and other metals. Most copper nuggets found in Arizona are relatively small, ranging from small sub-gram nugget to the larger pieces weighing a few ounces in size.
The area best known for quality copper nuggets and specimens is the Keweenaw Peninsula in northern Michigan. If you are interested in metal detecting for a true “trophy” piece of copper, this is the place to do it. Some of the largest copper nuggets found in Michigan have weighed several tons, and large pieces weighing 10 to 40 pounds are still found today, with smaller nuggets weighing a few ounces being quite common. The earliest known metal artifacts in America were made from copper by native tribes over 7000 years ago, and prospectors in Michigan can still find plenty of copper today.
Native copper comes in many interesting shapes as well, and can actually have a striking resemblance to high-grade gold nuggets and specimens. Of course the color is different, but many of them are rounded like placer nuggets, and quality specimens can also have crystalline, dendritic, spinel, octahedrons, and other interesting shapes. Typical copper nuggets bring a modest premium over their metal value, but many high-grade copper specimens can sell for several hundred times their metal value. In fact, as a premium based on the metals value, copper specimens often sell for many times more than gold does on a percentage-by-weight basis.
Copper is commonly associated with gold, and it can be found in many states in the U.S. Prospectors should be aware that they are out there, and nice specimens can have a collectable value, so be sure to take care of any copper specimens that you find. If you get into an area that you are finding lots of copper, be sure to search the area hard, since gold nuggets are commonly found in the same areas.
Gold collectors should also be aware that there are fake gold nuggets on the market, made by coating natural copper nuggets with a thin layer of 24k gold. They are surprisingly realistic fakes, but there are simple ways to identify them so be sure you can tell the difference. You can learn more about these gold plated copper nuggets in our fake gold nuggets article