The Story of the Upper Peninsula’s Bacon Rock
Please Note: The text below is a modified transcript of the above video. For the best experience, I recommend watching and/or listening to the video if possible.
Okay, story time!
Recently, my husband and I were out exploring an old copper mine. (We were allowed to be there, for the record! It’s called Quincy Mine and is located near Hancock, Michigan.) We were out walking around and enjoying the weather and looking at the old buildings and having a good time, when suddenly, we rounded a corner, and he went, "Oh! The bacon rock!"
(I mean, yeah, I don't know what else you would call it.)
It turns out, he recognized this red-and-white striped rock from a trip he took in high school, and although we took a second and acknowledged how cool and how interesting it was, I didn't really think that much about it... until later that night.
I was researching an idea for a completely different project when I came across this knowledge: The bacon rock is most likely the result of microscopic life from at least... 500 million years ago.
So, here's how you start with a bunch of microbes and end up with a rock that looks like breakfast.
Believe it or not, the official name of this rock is not "the bacon rock." It's actually Jacobsville sandstone, and for a while, it was pretty culturally important as far as rocks go. It's what's called a Global Heritage Stone Resource, which is a designation given by a couple of big geoscience organizations to honor and raise awareness about stones that have been widely used in human culture.
The reason I ran into this stone at all, at an old copper mine of all places, is because it was super popular in architecture for about 30 to 40 years, starting in the 1880s. It was quarried on and around the Keweenaw Peninsula, especially around the town of Jacobsville, and it was used for hotels, churches, and all kinds of buildings in Michigan's Upper Peninsula, but also throughout the central and eastern United States. (For instance, the original Waldorf-Astoria Hotel in New York City was originally made of Jacobsville sandstone.)
This stone was eventually replaced by things like cement, but for a while, people were really interested in it. It’s a nice looking stone, and also, it's sturdy and fire-resistant, and pretty easy to build with.
My favorite part of the story, though, is why Jacobsville sandstone can sometimes look like bacon — because if you want to know that, you have to go back anywhere from about 500 to 900 million years.
Long ago, about a billion years ago, the Midcontinent Rift happened. During this event, the continent that’s now North America started to tear apart in the Midwest/southern Ontario region. And eventually, that tearing created a rift valley. Then, over the next hundreds of millions of years, this rift valley started to get filled in, as rivers brought sediment down from the nearby mountains.
Now, originally, these sediments were approximately sand-colored, but they did contain some of the element iron, which was key. See, eventually, groundwater began to flow through this sediment — and that groundwater contained dissolved oxygen. That oxygen reacted with the iron, and this reaction created iron oxides, a.k.a. rust! This process is called oxidation, and it's how most Jacobsville sandstone got to be that nice red color that made people build churches and luxury hotels out of it.
example of cyanobacteria
As for the white, bacon-y marbling, though... well, according to newer hypotheses, that may have come from life.
Like a lot of things in science, this is something we are still learning about. That said, newer hypotheses propose that these white spots and white stripes were places where there was organic material — essentially, some kind of material that contained carbon that came from life. And that life was probably something microscopic, like cyanobacteria.
The thinking goes that because of its chemistry, these organic materials prevented oxidation from happening, so any iron in these areas never reacted with the dissolved oxygen, and it never created those red compounds. And so, the sandstone got its white spots and its white stripes!
(Aside: A small thing I also love about this is that these microbes would've lived on an Earth virtually unrecognizable to me. Geologists are still trying to figure out exactly how old the Jacobsville sandstone is, but depending on when these rock layers formed, these microbes could've lived on an Earth with 18-hour days, or they could've lived near a supercontinent, or they could've lived on a planet where there was basically no breathable oxygen in the air. And now, their legacy lives on decorative stones on an old boiler house in northern Michigan.)
When we came across this bacon-patterned rock, I absolutely was not expecting to spend time researching it — but I’m truly glad I did. It’s another one of those small, ancient, incredible stories that made me fall in love with the Upper Peninsula of Michigan in the first place.
