what you are saying is igneous rocks, not sedimentarhy. I get mine from a gravel pit a mile from where I grew up, and if unsure, knock them together. Bouncing may not work all the time. The other thing is you are not really supposed to take rocks from BWCAW, although it is done. Lots of good choices outside of area, and most people are happy to have you take them.
what you are saying is igneous rocks, not sedimentarhy. I get mine from a gravel pit a mile from where I grew up, and if unsure, knock them together. Bouncing may not work all the time. The other thing is you are not really supposed to take rocks from BWCAW, although it is done. Lots of good choices outside of area, and most people are happy to have you take them.