The use of the troy ounce in denominating the weight of copper was intended as an offhand joke, as troy ounces are generally used only in reference to precious metals. This coin was made in 2006 and is historically significant in the bullion trade as it was the first ever use of troy ounces as the weight designation of copper bullion. The reverse side depicts the still-standing Quincy #2 shaft-house, a National Historic Site, viewed from the south. On the obverse is a high relief image of a miner with pick, oil lamp, and pipe. The piece was minted from a massive blank weighing 36 grams of pure. To some degree light porosity is tolerated for 18 th century copper coins, but later issues are expected to be devoid of such flaws.A solid copper bullion coin honoring the famous Quincy Mine in Hancock, Michigan, located on the scenic Keweenaw Peninsula. Defects like green oxidization (also known as verdigris) and rough surfaces are considered highly detrimental for copper coins and will greatly diminish a coin’s value. It’s important to note that copper can oxidize incessantly to the point of making a coin porous, corroded and/or environmentally damaged. Many early coin albums contained sulfur, which can rapidly accelerate a copper coin’s transformation. Even if a red copper coin is plucked from circulation, it still might tone if stored in a reactive holder or album. As coins circulate, they come in contact with humidity and moisture-not to mention human hands. Why do copper coins shift in color? For coins, there are two common triggers: moisture and sulfur. These colors may knock a Red coin down to Red Brown or Brown, but they can enhance a coin’s eye appeal, grade and value. In addition, sometimes toned copper coins can take on attractive purple, blue, green and turquoise coloration. Even after a copper piece has turned brown, it can still retain strong luster. A Brown copper coin can still have traces of mint red, but only very small amounts. If virtually all of the original mint red has vanished, the designation “BN” or “Brown” is used. The RB designation covers a wide range of colors, ranging from “near-miss” coins that are mostly red to coins that are predominantly brown with minor amounts of red left. Coins that still retain some (but not all) of the original mint red, the designation “RB” or “Red-Brown” is applied. In order to qualify for the RD label, virtually all of the orange-red color must be intact save for some extremely minor spots or flecks.Īs copper coins begin to oxidize and tone, their color generally turns to a brownish hue. Copper piece retaining full original mint color are designated as “RD” or “Red.” This designation is listed immediately after the coin’s grade, i.e. With that in mind, numismatists have devised specific designations to describe a copper coin’s color.Ĭopper coins, when newly struck, display a bright, vibrant orange-red color. While silver, gold and (to a lesser degree) nickel are reactive to some degree, copper is the most likely to oxidize, tone and change in color. Of all the metals used for United States coins, copper is perhaps the most chemically volatile.
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