Silver has been mined for thousands of years for use in jewelry and coinage. Today, however, only a small percentage of the world production goes to coinage, and only about 10 percent to jewelry, silver plate and sterling ware. At one time, more than 40 percent of all the silver produced was used in photography because of silver’s sensitivity to light, but with the coming of digital photography, now that has waned. Although the main industrial ore of silver is acanthite, this valuable metal does sometimes occur in its native state.
Elemental silver occurs with acanthite in hydrothermal veins and in the oxidized regions of ore deposits, where it is formed through the action of hot waters on silver sulfides or of arsenides on silver chloride. Among the other minerals with which it may be associated are cobaltite, copper, galena, gold, and quartz.
Crystals of silver conform to the cubic system. Individual crystal specimens are extremely rare, but those that do occur tend to appear in cubes, octahedrons, or dodecahedrons. The metal more commonly appears in massive and disseminated grains, plates or wires. These can form coiled clusters that resemble ram’s horns. Other characteristic habits include arborescent sheets and scales.
Silver is a better conductor of heat and electricity than any other metal and is second only to diamond in the mineral world. Next to gold, it is also the most malleable and ductile metal known. It is harder than gold but softer than copper. This softness limits its use, even for coinage, unless it is alloyed with about 10 percent copper. When alloyed with 7.5 percent copper, it is known as sterling silver.
The largest active silver mine in the United States is near Virginia City, Nevada. Canada has productive mines in British Columbia, near Sudbury and Cobalt in Ontario, and in the Yukon. Native silver has been found at the Utica Mine near Keremeos, on Lightning Peak east of Vernon, and at Springer Creek in the Slocan Valley.
An exhilarating new find in 2018 that represents the largest group of native silver nuggets in the world were recovered near Globe, Gila County, Arizona. These enormous natural specimens of precious silver weigh 610 pounds collectively, or 8,896 troy ounces. The largest silver boulder weighed 417 pounds when it was unearthed, and now, after cleaning, tops 411 pounds.
The term nugget may be more appropriate, defined as a solid, native lump of precious metal. We are more familiar with gold nuggets, which range from a few grams to huge native gold specimens. In comparison, the world’s largest surviving gold nugget is the Pepita Canaa (Canaan Nugget), mined in Brazil in 1983, which has a gross weight of 60.82 kilos (134.10 pounds) and contains 52.33 kilos, or 1,682 troy ounces of gold. So, compared to the largest surviving gold nugget, the silver nuggets recently discovered are two to three times larger, and fall into the boulder-sized category. Still, maybe they should rather be called “mega-nuggets.”