Why was placer mining the most widely used method for mining for gold?

Because it was affordable to a large number of prospectors.

Explanation:

Placer mining was the most widely used method for mining for gold because it was affordable to a large number of prospectors. Placer mining is a method that uses water to excavate, transport and recover heavy minerals from deposits. It was widely used to find gold during the Gold Rush. The method takes advantage of the fact that gold has a higher density than the lighter siliceous materials with which it is found. This causes gold to sink more rapidly than the other materials.

Placer mining was the most widely used method because it was affordable to a large number of prospectors.