Lake Superior Agates
Lake Superior Agates are a specific kind of stone that was formed by volcanic activity along the North Shore 1.2 billion years ago. Gas pockets in the molten lava filled with mineral deposits like ferric iron, quartz or calcite as the years passed by. The pockets that were filled with quartz-rich deposits gradually crystallized into concentric bands (known as chalcedony) to form agates. Over time (we’re talkin’ a billion years) the agates were freed by water and ice from the lava rocks that they were buried in. Now, you’ll find them scattered along the North Shore.
Lake Superior Agates are red, orange and (sometimes) yellow and are very different from other types of agates found throughout the world. The oxidation of iron created the beautiful and iconic red colors. The color that appears between an agate’s band is determined by the amount of oxidation that took place when the rock formed.
Agates range significantly in size with most of them being small, pea-sized stones. However, some weigh over 20 pounds (they’re about the size of a bowling ball)! There are a few different types of Lake Superior Agates, with the most common being the fortification agate which displays the well-known banding pattern.
How to find Agates
When you’re searching for agates among other rocks, you’ll want to look for a few clues:
- Stones that appear shinier and more translucent than others around it
- Stones with colored bands
- Rust-red or yellow stained rock surfaces (caused by iron oxide)
- Surface that has a pitted texture
Where to Look
Agates can be found along Lake Superior’s North Shore, inland near lakes, almost any place with gravel or exposed rocks and the gravel banks of nearby streams and rivers. Lake Superior beaches along Highway 61 that we recommend for agate hunting include:
- Brighton Beach, Duluth
- Burlington Bay, Two Harbors
- Flood Bay Wayside (1 mile east of Two Harbors)
- Cut Face Creek Wayside Rest (14 miles north of Lutsen)
- Mouth of Devil Track River (3.7 miles east of Grand Marais)
- Five Mile Rock Beach (5 miles east of Grand Marais)
- Mouth of the Kadunce River (12.7 miles east of Grand Marais)
- Paradise Beach (13 miles east of Grand Marais)
- Brule River (14.5 miles east of Grand Marais)
- Horseshoe Bay (24 miles east of Grand Marais)
Back in 1969 the Lake Superior Agate beat out other types of rocks like Binghamite yellow silkstone, Thomsonite and Pipestone to become Minnesota’s state rock.