gold diamonds and natural geological wealth underwater

[DetectorGuy]

I checked with my mom and it is Anorthosite. I guess the purest form of it on earth is on the west bank of the bay in Grand Marais. The area you were rock climbing was it Palisade Head or Shovel Point? As far as the 3M sandpaper, a couple years ago I dove a 3M dock crib from 1902 near shovel point where they mined corundum for grinding wheels. The cribs are still there and it is very very close (150') to the "cave of the winds dive site". To get to the site from shore you could park on the shoulder of Hwy 61 near the intersection of Hwy 1 just North of Tettegouche State Park. Just South of here is Shovel Point. It is not named because it looks like a shovel but because a barge carrying shovels sank there and the shovels are rumored to be all over the bottom. Here is a link to that dive trip: