Mining for emeralds is delicate work. These gemstones are often hidden in other, less valuable, rocks. The best emeralds are usually found close to the earth's surface, making initial exploration a dainty task. Exploration is best done by hand, since machinery could destroy or blast away the stones.
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Unlike diamonds, rubies and sapphires, emeralds are not found along riverbanks. They are embedded in rocks, making their retrieval difficult. Complicating things further, emeralds might be hidden in rocks among layers of mica schist, a flaky, thin mineral. Cutting through the mica may be the only way to reach a hidden emerald inside.
One way to mine emeralds is through the open-pit method. Workers dig a large pit about 12 meters deep and then blast the surface with water to reveal mineral-bearing rocks. In the open-pit mining method, a lot of waste rock must be hauled away. The mining area is literally shaped like a pit that can hold equipment and workers.
Terrace mining is similar to open-pit mining in that a large hole is dug as deep as 12 meters. In the terrace-mining method, though, steps or "benches" are created parallel to the pit on the way to the bottom. The benches can be used as exploration spots, where miners search for emerald-rich rock, or they can be used to haul away waste rock. This method is used for emerald extraction in Colombia.
Some emeralds are harvested through tunnel mining, which involves digging a tunnel through the earth's surface to a vein of emerald-bearing rock. These tunnels can be very small–large enough to fit just one person and a pickaxe. Or they can accommodate larger equipment. According to the Mineral Gallery website, when rumors started flying of emeralds lying close to the surface in a small town in Brazil, people dug small tunnels in backyards and lowered miners on ropes to retrieve gemstones.
Blasting equipment isn't a good equipment choice for mining emeralds because the gemstones are close to the surface and may be hidden by other minerals. The work of extracting emeralds can be painstaking and delicate. Mines in North Carolina give tourists mesh screens to sift through already-mined gem dirt. Emeralds have been mined for hundreds of years, long before the discovery of electricity and mechanized mining.