Lighthouse Beach: Rockhounding in Saint Clair County, Michigan

Quick details

Access

Public area

County

Saint Clair County

State

Michigan

Coordinates

43.00712, -82.42259

Geology at Lighthouse Beach

This spot sits on Antrim Shale, mapped as black shale that formed roughly 385 to 360 million years ago. Sedimentary rock like this erodes unevenly, so the most productive collecting is typically along fresh cuts, badland slopes, and active drainages.

Mapped unit

Antrim Shale

Age

385–360 Ma (Late Devonian)

Rock types

black 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 Lighthouse Beach

Best months: April to November. Typical highs run 81°F in midsummer and 31°F in midwinter, with winter lows near 20°F.

Climate normals: NOAA 1991-2020 monthlies, PORT HURON station (2 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