Been out probing those river holes this year. I feel like my carrots paid itself off now! The 5 along the knives on the left are all marked 14k. Nice patina from sitting at the bottom of a hole full of hematite, nails, chain links, and such.
Holes in river rocks act like natural sluices,heavy stuff gets trapped while lighter sand and rocks gets blasted out. They're good places to find bullets, sinkers, and the occasional gold!