Editing Placer mining (section)

===Dry washing===
{{main|Drywasher}}
Sluicing is only effective in areas where there is a sufficient water supply, and is impractical in arid areas. Alternative methods developed that used the blowing of air to separate out gold from sand. One of the more common methods of dry washing is the Mexican dry wash. This method involves placing gravel on a riffle board with a bellows placed underneath it. The bellows is then used to blow air through the board in order to remove the lighter material from the heavier gold.<ref>{{Cite book|title=Finding Gold in the Desert: the Art of Dry-Washing|last=Lynch|first=O.|year=2001}}</ref> The amount of gravel that can be processed using the Mexican dry wash technique varies from 1 1/2 to 4 cubic yards per day, and can be processed at a maximum efficiency of 80%.<ref>{{Cite book|title=Placer Mining in Nevada|last=Smith|first=Alfred Merrit|publisher=University of Nevada Bulletin|year=1932|location=Reno, Nevada}}</ref> Another form of dry washing is "[[winnowing]]". This method was most commonly used by Spanish miners in America, and only requires a blanket and a box with a screen on the bottom. The material is first filtered through the box so only the finer material is placed onto the blanket. The material on the blanket is then flung into the air so that any breeze can blow away the lighter material and leave the gold behind. While this method is extremely simple and requires very few materials, it is also slow and inefficient.<ref name=":0" />