Precious Stones

I take slow, deliberate steps along the shore of Lake Superior with my head cast down, gaze sweeping methodically across the ground. Thousands of small pebbles are scattered in tiers on the sand, some glistening at the edge of the ebbing waves, others pushed further up the beach by past storms. They create a colorful earth toned mosaic punctuated by bright flecks of mustard, terracotta and slate blue.

My eye is most easily drawn to the layered nuggets of maroon and gray, which glow like hot embers in the shallow water. These rocks known as banded iron formations were created in the region two billion years ago when oxygen first became abundant in the atmosphere. This element combined with dissolved iron in the oceans to form iron oxides. The oxygen was produced by photosynthesizing algae, thus preserving the first breath of plant life in stone and laying the future economic foundation of this entire region.

I spy an oval shaped slip of white rock scored with telltale tubular striations contrasting against the grainy brown sand. It is a piece of fossilized coral from the ancient shallow sea that covered this land 400 million years ago. I imagine a watery world blanketed with coral reefs. Sea lilies sway in the current as the perfectly spiraled shell of an ammonite jets by, squid-like tentacles streaming in its wake. Trilobites scuttle across the sea floor over and around clusters of brachiopod shells. A seagull’s call brings me back to the terrestrial present, but thoughts of geologic time and transformation continue to swirl in my mind.

I am determined to collect a rainbow of rocks. Oranges and blues are mostly igneous rhyolite and basalt deposits from a 1,200 mile long rift through the heart of North America that opened up one billion years ago. It extended from modern day Ontario down to Kansas and branched over into Michigan. A large basin formed at the junction of the northern and eastern arms of the rift, which was ultimately filled with water by retreating glaciers to form Lake Superior just 10,000 years ago. I add them to the metamorphic green epidote and yellow chert already in my pocket.

Red, brown, purple and white sandstones represent deposits from ancient rivers and streams that flowed off the volcanic mountain ranges in the region 500 million years ago. The brown sandstone was particularly prized by architects in the late 1800’s as a building material, referred to as Lake Superior Brownstone, and was used to construct many stoic buildings and residences in the towns that ring the lake. These sandstone formations were also carved and smoothed by wind and waves to form the Apostle Islands.

The individual colors of rock all blend to steely gray as twilight approaches. I sit on the beach listening to the hush of the waves lapping onto shore, holding the accumulation of two billion years in the palm of my hand. Sunset casts its glow as the lights of Washburn begin to twinkle in the distance. I dig my toes down into a confetti of geologic time to feel the lingering warmth of the radiant summer sun still in its grains.