. Amazon.com: Customer reviews: Portable Rock Crusher - Gold ... This rock crusher does a fine job. It will crush small 0 in. X 0in. rocks into dust in a matter of a minute. Although very small pieces of rock remain intact, they are small enough to either use a pestle and mortar to pulverize them or leave them as they are and pan them separately You certainly will be able to recognize any possible gold still trapped within them.. 