gold diamonds and natural geological wealth underwater

[DetectorGuy]

The crinoid fossils near the Ford dam and hidden falls area are fairly easy to find.
  As far as agates go... The ones in Mille Lacs were places there when the glaciers came by. these would be just dumb luck to find. If you want to find Agates with out luck you need to go to the source, lava flows. lava pushed these agates up from deep in the earth and later picked up by the glaciers and dropped in various spots (glacial till). Along the North shore there are lava flows still visible both above and below the surface. Agates are still embedded in these lava flows if you look hard.
  Thompsonite is found all along the North shore North of Two Harbors.
  There is a very rare rock only found near the Split Rock Lighthouse... and I can't remember the name of the stone. it is so rare that it is only found in two places on earth: near the Split Rock Light House, and somewhere in Europe. It is also found on the moon from the books I've read.
  Gold. There have been some findings of placer gold near the Red River Valley.