Dolostone: Illinois State Rock!

In 2022 dolostone was declared the official State Rock of Illinois. This web page is being developed as a source of online resources related to an exhibit celebrating dolostone at the Kids Korner booth at the 2023 Chicagoland Gems & Minerals Association show.

The goal of the exhibit: Every time you see a pile of crushed stone on a Chicagoland street, you will think, “That could be dolostone, the Illinois State Rock. And there’s a 430 million-year-old story behind every stone!”

See this pile of crushed stone and think, “That could be dolostone, the Illinois State Rock. And there’s a 430 million-year-old story behind every stone!”

These two photos show a mock-up of the exhibit we will display at the Kids Korner booth on May 27 and 28. (The finished exhibit will no doubt look a little different.):

The free specimens that we will give away at this exhibit come from the underground mine at Federal Quarry in McCook, Illinois. Thank you to Heidelberg Materials for donating the specimens!

The Kids Korner exhibit condenses a huge amount of information into eight brief labels. If you want to learn more about dolostone and how it became the State Rock of Illinois, check out these online news stories:

From WTTW: Meet Dolostone, Illinois’ New Official State Rock: ‘This Immense Story Hiding Underneath Our Feet’

From the Chicago Tribune (there may be a pay wall): Like Charlie Brown on Halloween, Illinois got a rock, thanks to students at Pleasantdale Middle School in Burr Ridge — an official state rock

If you want even more details, then let’s go back 430 million years to the Silurian Period, long before dinosaurs walked the Earth. The crushed stone in that photo above came from a quarry in the Chicagoland area. The quarry was dug into solid rock that formed in the shallow sea that covered Chicagoland during the Silurian Period. A good place to explore the Silurian Period online is this joint Field Museum/Milwaukee Public Museum website, The Virtual Silurian Reef.

Or, if you are into books, you should get a copy of Silurian Journey: Adventures in a Prehistoric World from the Paleontological Research Institute. (We will have examination copies at the Kids Corner booth.)

Here are a few online resources about dolostone quarries in the Chicagoland area. (Note that these articles sometimes use the term “dolomite” instead of dolostone.):

  • From the Earth Science Club of Northern Illinois (ESCONI), here’s an article about dolostone as a building stone in Chicagoland: One Stone to Another by Joe Kubal.

(We will be adding more resources soon.)