Lake Huron Roadside Park: Puddingstone & Gowganda Tillite Rockhounding in Sanilac County, Michigan

Updated August 2026

Lake Huron Roadside Park is a mapped rockhounding spot in Sanilac County, Michigan. Reported finds include puddingstone, gowganda tillite, stinkstone, quartz, charlevoix stone, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Sanilac County
State: Michigan
Coordinates: 43.40418, -82.53921

Geology at Lake Huron Roadside Park

This spot sits on Coldwater Shale, mapped as shale that formed roughly 360 to 325 million years ago. Sedimentary layers like these are where fossils are typically preserved, and fresh exposures after rain or in active cuts tend to produce best.

Mapped unit: Coldwater Shale
Age: 360–325 Ma (Mississippian)
Rock types: shale
Elevation: 570 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Best time to visit Lake Huron Roadside Park

Best months: April to November. Typical highs run 78°F in midsummer and 30°F in midwinter, with winter lows near 16°F.

Climate normals: NOAA 1991-2020 monthlies, LEXINGTON WTP station (10 mi away).

Land & collecting status

Generally open to casual rockhounding

Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

State guidance last verified: April 1, 2026

Michigan DNR — Rockhounding rules
Michigan Geological Survey
Isle Royale National Park — Rules
Community submissions reviewed against published agency rules

Found at Lake Huron Roadside Park

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

Nearby rockhounding spots

Other rockhounding spots within driving distance of Lake Huron Roadside Park.

Lake Huron Roadside Park FAQ

Where is Lake Huron Roadside Park?+

Lake Huron Roadside Park is in Sanilac County, Michigan, at 43.40418, -82.53921.

What rocks and minerals can you find at Lake Huron Roadside Park?+

Lake Huron Roadside Park is reported to produce Puddingstone, Gowganda Tillite, Stinkstone, Quartz, Charlevoix Stone, Horn Coral, Brachiopod, Petoskey Stone.

Is collecting allowed at Lake Huron Roadside Park?+

Generally open to casual rockhounding. Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Lake Huron Roadside Park?+

A rock hammer, a cold chisel, safety glasses, and newspaper or foam for wrapping finds cover most fossil ground. A trowel and a sieve help in soft exposures.

When is the best time to visit Lake Huron Roadside Park?+

The most comfortable months at Lake Huron Roadside Park are April to November.

How do I get to Lake Huron Roadside Park?+

Open the directions link to navigate to 43.40418, -82.53921 in Google Maps. Some spots are remote, so check road conditions before driving out.

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Open Lake Huron Roadside Park on the map

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