Most higher-grade metallic ores are usually found very close to the Earth's surface, typically less than 1,000 feet underground. Shallow deposits are often more economically viable to extract compared to deeper ones, which require more complex and costly mining methods. Therefore, the statement that they are usually found very close to Earth's surface is the most accurate.
To clarify the other statements:
- Many ores may require drilling, especially in exploration or extraction processes.
- While some ores may be found deep underground, high-grade ores that are economically feasible to mine are often located closer to the surface.