Two questions about gold's behavior Options

[Sword]

I have two questions that have been bugging me.
1: Has fast does flake/flour gold sink? If I have a pan, and I shake it for 5 seconds is all the gold on the bottom? 30 seconds? I am wondering about scraping off the top section to speed panning.

2: Does flour/flake gold sink all the way to the bottom of a river? Related to this, how far down is 'bedrock' I know 'it depends' but roughly how far typically, a few feet, 20 feet? How can I tell when I hit bed rock? I have gotten to where I am hitting tight rocks bigger than my hands but I can still slowly dig through this.