Ely Greenstone dates from the Precambrian Age, Archean Eon, Neoarchean Era, some 2.722 billion years ago. It is a type of of Banded Iron Formation (BIF), formed when metamorphosed basalt oozed onto the ocean floor into bulbous forms or “pillows.”
Iron-rich Ely Greenstone has BIF’s characteristic “banding,” in most cases rusty red or pearly white. It is fine-grained and heavy. The slab shown here weighs 19.8 pounds (8.981 kg). Its origin as “pillow lava” gives this piece an odd, serpentine shape.
Great Lakes rock hounds are particularly grateful for the glaciers that dumped myriad rocks and fossils in their wake. On the beach at Lake Michigan’s west coast, the gorgeous deep teal of wet Greenstone stands out among the millions of plain limestone rocks.
We can’t wrap our minds around the deep time 2.722 billion years represents. Holding in your hands something so old is a transcendent, mystical experience. It reminds us that humans are a only a smudge on Earth’s timeline.
About the Author
Elizabeth G Fagan is an artist who resides on Lake Michigan’s shoreline in southeastern Wisconsin—a place she calls Lake Michigan’s Left Coast. She was a professional writer based in Chicago for much of a professional career that spanned more than 25 years.
The 2012 superstorm Hurricane Sandy is remembered for devastating New York City. Sandy was so massive she caused 25-foot waves on Lake Michigan in Chicago, some 900 miles to the west. Millions of stones washed up onto Montrose Dog Beach, the place where Fagan regularly walked her German Shepherd Rosie. One of Fagan’s early interests was revitalized as she collected rocks and fossils on that beach.
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