Bay Furnace Ruins: Slag & Hematite Rockhounding in Alger County, Michigan

Plan your visit

Confirm rules before collecting

County

Alger County

State

Michigan

Postcode

49862

Coordinates

46.44180, -86.70557

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

Land & collecting status

Confirm rules before collecting

Land status here is not confirmed. Verify with the managing agency before collecting, federal, state, and tribal rules differ.

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.

Best time to visit Bay Furnace Ruins

Comfortable months (45 to 90°F highs)

Best months: April to October. Typical highs run 73°F in midsummer and 24°F in midwinter, with winter lows near 12°F.

Climate normals: NOAA 1991-2020 monthlies, MUNISING station (3 mi away).

Geology at Bay Furnace Ruins

This spot sits on Jacobsville Sandstone, mapped as sandstone that formed roughly 1600 to 1000 million years ago. Tough silica like agate, jasper, and chert typically weathers out of beds like these and collects as float in drainages and on deflation surfaces.

Mapped unit

Jacobsville Sandstone

Age

1600–1000 Ma (Mesoproterozoic)

Rock types

sandstone

Elevation

610 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.

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