USA HISTORY

Detailed explanation-1: -Panning works best when gold is coarse and well liberated. Under right conditions, panning can produce high grade concentrates or even liberated gold. Then miners can employ gold recover methods such as direct smelting (described below), although many panning operations lead to directly recoverable gold.

Detailed explanation-2: -Gold can be freed from these ores or concentrates by treating them with various oxidizing processes. The most common method is to roast gold-bearing minerals at temperatures of 450° to 750° C (840° to 1, 380° F) to destroy the interfering sulfides.

Detailed explanation-3: -Hydraulic mining was a variation on ground sluicing where the water delivered to the site would be shot through a nozzle at high pressure onto the face of the cliff, thereby washing away tons of boulders, gravel, dirt, and, in the hopes of the miners, ounces of gold.