About
About this guide
A free, neutral, independent guide to Michigan geology and rock hunting.
Who runs it
This guide is run anonymously by Michigan rock hunting enthusiasts. It is not connected to any business, club, shop or agency. There are no ads and no affiliate links.
How facts are checked
- Facts come only from official or authoritative sources: Michigan DNR and EGLE, the Michigan Legislature and Administrative Code, the National Park Service, the USDA Forest Service, federal regulations, the USGS, the Michigan Geological Survey, and university museums and departments.
- Rules are quoted word for word, with a link to the official text and the date they were last checked.
- Geology is explained in plain English, keeping every number, age and name exactly as the source gives it.
- Geologic ages follow the International Commission on Stratigraphy chart.1
- Anything that could not be confirmed at an official source stays off the site until it can be.
- Places are listed only when an official source names them. A pin on a map or a forum post is not enough.
- Sources are listed at the bottom of every page. Every photo is credited on the photo credits page.
Send a correction
If you find an error or an outdated rule, please let us know.
Sources (1)
- International Commission on Stratigraphy, International Chronostratigraphic Chart, v2026/06 (PDF). https://stratigraphy.org/ICSchart/ChronostratChart2026-06.pdf (checked October 21, 2026)