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Rockhound Road Trip

Rock Picking

Beaches and gravel roads alike beckon geological treasure hunters

The members of the species Rockhoundicus sapiens can be found throughout northern Minnesota and northwestern Ontario, particularly on gravel roads and pebble beaches. You will often see them hunched over at the water’s edge, picking through wet rocks with the patience and focus of an archaeologist sifting fingernail-size pottery fragments from a dirt pile. They often travel in family groups.

Pseudo-scientific kidding aside, hunting for natural treasures is a time-honored northern pastime perfect for a summer afternoon. The Northern Wilds has geological treasure to tempt any rock picker, whether you get a thrill from the jewel-like beauty of an amethyst, the banded brilliance of a red agate, or the deep-time significance of a Cretaceous-period trilobite.

Amethyst Ontario’s Official Gemstone

Deriving its name from the Greek word amethystos (“not drunk”), amethyst is a type of quartz ranging in color from clear to vivid purple that is mined throughout the world, from Jurassic-age formations in southeastern Brazil to the Ural Mountains of Russia. Thunder Bay is home to the largest amethyst mine in North America.

Amethyst was once considered a rare and precious gem, alongside diamonds and rubies, until the discovery of massive amethyst deposits in South America and elsewhere drove prices down. Amethyst is found in both geode and “toothy” form. At several locations in Thunder Bay, including Amethyst Mine Panorama, you can purchase or dig your own purple gem.

Thomsonite Lava Bubbles

A rare and distinctive zeolite mineral found in a handful of places in the world, including the Faroe Islands, Nova Scotia and India, thomsonite is named after Thomas Thomson, the Scottish chemist and minerologist who first identified it in the early 19th century. Thomsonite forms mainly in gas bubble cavities in the kind of basalt that occurs on the North Shore. North Shore thomsonite is known for its coloring, with many displaying richly colored concentric rings reminiscent of agate eyes or leopard spots. Unlike agates, thomsonite specimens are rough, not naturally polished-looking. Tumbling brings out their strange beauty. You can marvel at polished specimens and purchase your own at Thomsonite Beach Inn and Suites in Grand Marais.

Mary Ellen Jasper Ancient Algae

Named for the place it was first discovered – the now-defunct Mary Ellen Mine in Biwabik – Mary Ellen jasper is a striking red “stromatolitic ferruginous chert,” a fancy way of saying it is iron-rich and composed largely of wavy columns of fossilized cyanobacteria, or oxygen-generating algae. This particular algae lived some 2.3 billion years ago, growing in the shallow sea that once covered much of North America and enriching the earth’s atmosphere with the oxygen we now enjoy. (Thanks, cyanobacteria!) For another example of ancient sea life, keep your eyes peeled while hiking in Ontario’s Kakabeka Falls Provincial Park for tawny bands of stromatolites in exposed outcroppings of the Gunflint Formation.

Fossils Beware of Giant Beaver

While you won’t find a Tyrannosaurus rex while digging a spot for your new petunias this summer, certain areas in the Northern Wilds do hold fossilized remnants of our ancient past. At the Cretaceous Ore Pile in Hill Annex Mine State Park near Calumet, for example, you can find trilobites, shark teeth, coral and other marine life from about 100 million years ago. In glacial till (rocks scraped up and scattered by glaciers) throughout Minnesota, a sharp-eyed fossil hunter could score a mastodon tooth or even a bone from a giant beaver.

Lake Superior Agate Glacier-Polished Gemstone of Minnesota

Lake Superior Agate

A perennial favorite of rockhounds, Lake Superior agates come in multiple colors and distinct patterns, including “fortification agates” and parallel-banded “water-level” agates. They are the state mineral of Minnesota and their formation encapsulates the geologic history of the North Shore.

When the massive basaltic lava flows that form much of the North Shore first flowed, they were pocked with bubbles of gas. The lava cooled and hardened. Later, water and liquified minerals flowed through the gas pockets and crystallized. Glacier action during the last Ice Age scattered and polished the resulting minerals: the hard, glossy agates we know today. Moose Lake State Park in Moose Lake has a large agate display.

While beaches are unarguably the more scenic spot for agate-hunting, Lake Superior agates can also be found on gravel roads throughout northern Minnesota and beyond. In fact, the striking burgundy agate pictured was discovered on a gravel road in Duluth.

Beach Glass Trash to Treasure

From a purely functional point of view, beach glass – also called sea glass – is nothing but antique trash. Yet some beachcombers delight in finding these translucent gems, formed of glass shards tumbled in the rough currents of Lake Superior for so many years their sharp edges have been battered away. Beach glass comes in colors ranging from green, teal blue and sapphire blue to brown and even red.

Consult a sea glass guidebook (yes, they exist) for help in identifying your finds by color and identifying marks like stamps, ridges and mold lines. Along with glass pieces, smoothed pieces of ceramic may sometimes be found.

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