I am not an expert on gold but I have done considerable research on the gold rush in California. There are two general types of gold strikes. Lode gold is the gold that is found in rock mountains in quartz and placer gold is what has been washed away from it's original point of creation and "placed" in the rivers or soil where rivers used to run. Gold flakes that you pan for and nuggets are placer gold.
Gee I am glad you backed me on that one ole.grubstake. I know who you are and I knew you would answer the question so, not being an expert, I was a bit intimidated to write my response. I would really love to go to California and detect for gold...someday HH
HI might I add "eluvial" placers also? These are found on the steep slopes of mountains or hills. They are formed by freezing, normal earth movemets, rains, etc. Basically gravity does the forming./concentrating.