Rocks for Jocks (and Paddlers) — Part 2

While mining activities on Lake Superior have targeted commercially valuable minerals like gold, silver and copper, sea kayakers know there’s more that glitters on the coast.

Polished stones at Slate Islands.


Migmatite – Wavy folds of quartz take shape on smooth sheets of pink granite, revealing the blend of metamorphic and igneous rock that defines this formation. Migmatite is created when quartz and gneiss partially melt and flow into igneous rock, and then recrystallize (solidify) in a marbled pattern.

Where to see it: Agawa Bay (Lake Superior Provincial Park), Oiseau Bay (Pukaskwa National Park).


Agate – The glassy face of a piece of water-polished agate reveals endless patterns of soft, muted colours. Agate is typically found in volcanic formations, created when silica-based minerals such as quartz were heated and then crystallized in pockets contained in lava rock. An agate’s concentric rings demonstrate the cooling process.

Where to see it: Gargantua (Lake Superior Provincial Park), Michipicoten Island, Simpson Island (Lake Superior National Marine Conservation Area).


Columnar basalt – So-called “columnar jointing” of volcanic rock occurs only under specific environmental conditions. To create a “beehive” formation like the Giant’s Causeway in Northern Ireland, a lava flow cooled and settled in a similar manner to drying mud, creating vertical hexagonal fractures.

Where to see it: Simpson Island (Lake Superior National Marine Conservation Area)



Columnar basalt at Simpson Island.

To learn more, pick up a copy of Roadside Geology of Ontario: North Shore of Lake Superior by E.G. Pye.