 Along the lakeshore can be found quartz-banded thomsonite and agate gemstones created by mineral infilling of gas cavities formed when the lava flows cooled.Interior highlands include Eagle Mountain and the Misquah Hills.Most of the eastern part of the Superior National Forest and its Boundary Waters Canoe Area Wilderness (BWCA) is located on the Duluth Complex, and its exposed Late Precambrian bedrock formations are characteristic features of the region.