Jared goes to a flea market. At the flea market, he sees a rock dealer who is selling different types of rocks. Jared sees a nice looking rock, which he identifies as a quartz. Jared says to the rock dealer, how much for that quartz? The dealer states, that quartz is $20. Later Jared finds out that it is an uncut diamond worth $1,000,000. The dealer wants the diamond back. Can the dealer undo the contract?