Harrisville State Park: Granite & Chert Rockhounding in Alcona County, Michigan

Updated August 2026

Harrisville State Park is a mapped rockhounding spot in Alcona County, Michigan. Reported finds include granite, chert, quartz, chain coral, horn coral, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Paid / fee dig
County: Alcona County
State: Michigan
Postcode: 48740
Coordinates: 44.64750, -83.29764

Geology at Harrisville State Park

This spot sits on Sunbury Shale, mapped as black shale that formed roughly 420 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: Sunbury Shale
Age: 420–325 Ma (Devonian to Mississippian)
Rock types: black shale
Elevation: 630 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 Harrisville State Park

Best months: April to October. Typical highs run 73°F in midsummer and 26°F in midwinter, with winter lows near 13°F.

Climate normals: NOAA 1991-2020 monthlies, HARRISVILLE SP station (0 mi away).

Land & collecting status

Pay-to-dig site

This is a fee-dig location. Hours, prices, and what you can keep vary by operator. Call ahead before driving out.

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 Harrisville State 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 Harrisville State Park.

Harrisville State Park FAQ

Where is Harrisville State Park?+

Harrisville State Park is in Alcona County, Michigan, at 44.64750, -83.29764.

What rocks and minerals can you find at Harrisville State Park?+

Harrisville State Park is reported to produce Granite, Chert, Quartz, Chain Coral, Horn Coral, Petoskey Stone, Puddingstone, Yooperlite.

Is collecting allowed at Harrisville State Park?+

Pay-to-dig site. This is a fee-dig location. Hours, prices, and what you can keep vary by operator. Call ahead before driving out. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Harrisville State 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 Harrisville State Park?+

The most comfortable months at Harrisville State Park are April to October.

How do I get to Harrisville State Park?+

Open the directions link to navigate to 44.64750, -83.29764 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in Michigan

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Open Harrisville State Park on the map

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