Arastra's were rock-crushing machines with a center post and having a wooden bar or pole going out from the center post, and that being pulled around and around by an animal such as a burro. Connected to the bar was a rope or chain which was then connected to a large rock. That rock was thereby pulled around in a circle, slowly crushing ore rocks that were thrown into the area.

The pulversized ore was then collected and smelted down.

Arastras were first popular among Mexican miners beginning in the mid-1800's.