Step 1: Step 1 finding the rocks
Streams are great places to find rocks that make good paints for a couple of reasons. 1 They tend to contain a selection of stones and 2 the light ones that crush easily are usually on top. If you happen to be located in France there is supposedly the best Red Ochre in the world there.
Many of the stones that make good pigment are sedimentary but not all, malachite is a transitional I think and and there may some igneous pigments.
If you're in town not to worry just head out to your local lapidary and buy some, I've got a piece of Congolese azurite that is a absolute blue, but it's gem quality so I'll never use it for paint, but a guy can dream can't he.
OK you got me, it's not a stream it's a gravel road, but I got some great Kentucky Ochre on this road, like I said rocks are where you find them.