Question

What is true about most higher-grade metallic ores?

A. They are usually found deep below Earth’s surface—more than 1,000 ft underground.
B. They are usually found very close to Earth’s surface—less than 1,000 ft underground.
C. Most of them can be extracted using the placer method.
D. Most of them can be extracted without requiring drilling.

Answer 1

A. They are usually found deep below Earth’s surface more than 1,000 ft underground.

What is higher grade ore?

A higher grade means that the ore has a higher density of gold. Gold ore density is measured by grams per ton. Higher quality mines have densities of 8 to 10 g/t while on the other hand, the lower quality mines have densities of 1 to 4 g/t. Some of the world's highest-grade mines are present in the United States of America, Russia, and Peru. These ore bodies are lying more than 1,000 feet which is equals to 300 m.

So we can conclude that option A is the correct answer.

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