Beach Rocks


Rhyolite is high silica lava, quite common in the conglomerates of the Keweenaw and also in some small bodies along and near the Keweenaw Fault, like Mount Houghton. Rhyolite is a hard rock and makes smooth beach stones, usually reddish in color.

Flow-banded rhyolite

Geologic map of Mount Houghton, Keweenaw. This is the highest point in the peninsula. The red area is a volcanic dome.