Where: Midwest · North America · approx. 47.54, -90.1 (vicinity only)
Why this spot: thomsonite, agate
What turns up: The Lake Superior north shore near Grand Marais sheds eyed thomsonite pebbles from basalt onto a few gravel beaches.
Access: Open / legal.
Loose beach and float material is generally collectable; do not dig protected cliffs or take from protected sites. Confirm local rules and tides.
Open in Mudlark Map →
Satellite view, historic-map overlays, tide/flow context and field notes are in the app. Exact research detail is part of Pro.
Pins are approximate by design. This page is historical research, not permission to dig. Check ownership and local law first.