Is this Puddingstone?
Puddingstone is a conglomerate made of rounded pebbles or cobbles held in a finer-grained matrix, often with bright red jasper standing out against a lighter background.
Three quick checks
Look at both the pebbles and the matrix
Look for rounded pebbles or cobbles inside a finer matrix, strong contrast among fragments, and a natural matrix rather than the coarse binder found in concrete or asphalt.
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Find rounded pebbles
Look for separate rounded pebbles or cobbles held inside a finer-grained matrix.
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Look for contrast
Quartz, red jasper, chert, granite, and other fragments can create a colorful mix against the surrounding matrix.
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Check the matrix
Concrete and asphalt can look similar, but their matrix is usually coarser-grained and scratches more easily.
Many older pieces, cemented into one rock
Puddingstone is a conglomerate. Rounded pebbles and cobbles became embedded in a finer matrix such as sandstone or siltstone. Michigan Puddingstone is associated with material carried and deposited by glaciers, then left near the Great Lakes as the ice retreated.
Do not let pavement fool you Concrete and asphalt can mimic conglomerate. Look closely at the matrix, which is usually coarser and easier to scratch in the man-made material.
A colorful mix carried through Michigan
- What it is
- Conglomerate rock
- Michigan connection
- Associated with glacial deposits in Michigan
- Common fragments
- Quartz, red jasper, chert, granite
What would you like to do with it?
Take the full field guide to the beach
The Trading Post's field guide includes clear photos, a broader visual identification guide, tools, tips, and practical help for rockhounding around Lake Michigan.
