Skip to main content

Fast Five: EGLE geologist identifies Lake Huron rock, becomes Internet rockstar

Head shot of Mary Ann St. Antoine, EGLE environmental quality analyst

WBCK-FM in Battle Creek asked readers of its website to help Tina McKercher identify a rock she found on the shores of Lake Huron, near Harrisville. She got nowhere until Mary Ann St. Antoine, EGLE environmental quality analyst with a background in geology, saw the query and solved the mystery. This Fast Five edition of MI Environment digs deep into St. Antoine's interest in Michigan geology.

How long have you been interested in geology?

I absolutely love geology and my family and friends complain because all vacations turn into geology field trips. When you look at the geology, it's everywhere and I see things that I find so exciting everywhere I go. Unfortunately, not everybody shares my excitement!

I graduated in 1990 from Lake Superior State University (LSSU) with bachelor's degree in geology. They have an excellent geology program — all their sciences really. I grew up in Toledo and my father took us fossil hunting in the area and that's where I first saw the pyrite replaced fossils (similar to the rock that Tina found.) The identification of the rock is not a big deal at all — any geologist would have recognized it.

How did geology become part of your career?

My grandmother was from St. Ignace and we spent summers in the Upper Peninsula (U.P.) and I cried when I had to go home. I love the U.P., and it is one of the most beautiful places in the world. I moved to St. Ignace in 1976, married a local and raised my children here.

I worked at LMAS (Luce, Mackinac, Alger, Schoolcraft counties) District Health Department in Mackinac County in drinking water (geology related) in the 90s and then I worked at LSSU as the science lab manager for 15 years. I also worked as adjunct faculty teaching geology labs.

LSSU has a very field intensive curriculum and I went on most of their field trips — Ontario, Wisconsin, Appalachians, New Mexico, Arizona, Texas, Nevada, South Dakota, Wyoming, Montana, and California — and I really got to understand geology over the years.

I started at EGLE in 2014. It was a hard decision to leave LSSU as I loved working around the young people. I am an environmental quality analyst here at EGLE and part of my job is hazardous waste (which I also did at LSSU) but part of my job is as a geologist for landfills. EGLE is the best employer — ever! They offer Plan C which allows employees to take of leave of absence up to three months. So LSSU picks me up as a contract employee and I still go on a yearly LSSU field geology trip in May.

How did you learn of the quest to find out what Tina McKercher's rock is?

I saw the article when it popped up on my news feed for "Michigan News" and I quickly emailed her the answer to her question about her rock. I never thought it would cause so much hoopla! Pyrite nodules (or concretions) are pretty common. Pyritization of fossils is common in some areas of the Midwest — like the Devonian shale where I grew up in northwest Ohio. I had pyritized trilobites and brachiopods that I had collected as a child. I lived in a swampy area in the eastern U.P., and they rusted so I warned the woman in the article about long-term storage of her rock. Her find is very beautiful, and I haven't ever seen one just like that before.

Are you a rock collector?

I'm not a big rock collector compared to some people. I had a friend that taught 5th grade science and the rocks that I collected on field trips, I gave to her for her student display. I do pick few agates and pretty rocks along the beach and I collect "omars" (omarolluks) — a graywacke that has a hemispherical void from where a concretion dissolved. They just look cool.

What advice do you have for people who are interested in rock collecting?

My advice to anybody that is interested in collecting rocks is to always look down. I have found some beautiful agates in parking lot gravel. Rocks also show up in the most unexpected places.

The State of Michigan has lots of information on the web about geology and is a wonderful resource. A great book for laymen, available in many libraries, is Geology of Michigan by John A. Dorr and Donald F. Eschman. If anybody is interested in geology, I recommend it as a career, and LSSU has great program.

Photo posted by Tina McKercher on Facebook

Like this content? Follow us on Twitter at @MichiganEGLE or on


Take a short survey and let us know what you think about MI Environment.