Beach Rocks

Beaches underlain by basalt usually include a variety, some with spots, and some that are uniformly gray.

Basalts have bubbly flow tops, and these fill with a variety of colored minerals.  The rock itself often is a bit reddish (amygdaloid).

Often lava flows have rather uniform interiors which are gray in color, and beaches may be dominated by these.

Special Basalt types

Ophitic basalt or Ophite is common in the Keweenaw, and rare elsewhere. It is from the flow interior and has uniform spots which are usually lighter and harder than the rest of the rock.

Pegmatoid, pegmatitic basalt or dolerite is also found in the Keweenaw, and is very rare elsewhere. It is from the flow interior and has white crystals which are conspicuous.

Porphyritic basalt, sometimes called "turkey track" is a rare but distinctive type of basalt in the Keweenaw. Look for it near Keweenaw Point.

Basalt

Basalt is a dark gray rock which is often the dominant rock type on the Keweenaw North Shore. It varies from almost featureless to spotted.