When discussing higher-grade metallic ores, the following statement is generally true:
They are usually found very close to Earth's surface, less than 1,000 ft underground.
Higher-grade metallic ores are often located in deposits that can be accessed with relative ease, making it more economically feasible to extract them. While some ores can indeed be found deep underground, many valuable metallic ores (like gold, silver, and copper) are found closer to the surface, which makes open-pit mining and other surface mining methods viable.
The other statements are less precise or not true in general:
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Most of them can be extracted without requiring drilling: While some mining methods do not require drilling, many do, especially in hard rock mining operations.
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They are usually found deep below Earth's surface more than 1,000 ft underground: This is not accurate for most high-grade metallic ores, as mentioned above.
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Most of them can be extracted using the placer method: Placer mining is specific to certain types of deposits (such as those of gold and gemstones found in sediment) and does not apply to all metallic ores, particularly hard rock ores.
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