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

Updated August 2026

Bay Furnace Ruins is a mapped rockhounding spot in Alger County, Michigan. Reported finds include slag, hematite, banded iron formation, jaspillite, yooperlite, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Check locally
County: Alger County
State: Michigan
Postcode: 49862
Coordinates: 46.44180, -86.70557

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.

Best time to visit Bay Furnace Ruins

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).

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.

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 Bay Furnace Ruins

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 Bay Furnace Ruins.

Bay Furnace Ruins FAQ

Where is Bay Furnace Ruins?+

Bay Furnace Ruins is in Alger County, Michigan, at 46.44180, -86.70557.

What rocks and minerals can you find at Bay Furnace Ruins?+

Bay Furnace Ruins is reported to produce Slag, Hematite, Banded Iron Formation, Jaspillite, Yooperlite, Lake Superior Agate.

Is collecting allowed at Bay Furnace Ruins?+

Confirm rules before collecting. Land status here is not confirmed. Verify with the managing agency before collecting — federal, state, and tribal rules differ. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Bay Furnace Ruins?+

Most agate and jasper is surface float: bring a spray bottle, a pick or small shovel, and a sturdy bag. Wet stones show their banding and translucence.

When is the best time to visit Bay Furnace Ruins?+

The most comfortable months at Bay Furnace Ruins are April to October.

How do I get to Bay Furnace Ruins?+

Open the directions link to navigate to 46.44180, -86.70557 in Google Maps. Some spots are remote, so check road conditions before driving out.

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Open Bay Furnace Ruins on the map

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