Keweenaw Peninsula EarthCaches 

Ginormous Stamp Mill Ruins 

Connection to the Earth Science Curriculum

Essential Lessons:
  1. What was the purpose of the stamper?
  2. How was copper sorted from the rest of the poor rock?

Earth Science Literacy Principles

Big Idea 9: Humans significantly alter the Earth.

Common misconceptions

  1. People do not have a big impact on the environment. The environment will balance itself out.
  2. Mining and exploration cannot be accomplished safely with respect to the environment.

Michigan State Science Content Expectations Addressed

E.ES.E.5 Human Impact – Humans depend on their natural and constructed environment. Humans change environments in ways that are helpful or harmful for themselves and other organisms.

E.SE.E.3 Using Earth Materials – Some Earth materials have properties that make them useful either in their present form or designed and modified to solve human problems. They can enhance the quality of life as in the case of materials used for building or fuels used for heating and transportation.


Stamp Sands: Left over or waste rock that was stamped, or crushed, into course grain sands and dumped into Lake Superior and on surrounding land during the mining boom.

Poor Rock: The rock that was left over, or waste rock, and either dumped into piles near the mines or deposited directly into water.

Ore: Rock that contained copper or other wanted material/minerals

Stamper: The machines used to crush rock into smaller pieces to be sorted into ore and poor rock

Gravity: A natural force of attraction that acts on objects and draws them toward the center of the Earth.

Density: An object’s mass per unit volume. Example: If you were to hold a piece of copper in one hand and a piece of poor rock in the other, the copper would feel heavier in your hand


Osceola Township Board
PO Box 437
Dollar Bay, MI 49922

The Stamp Mill Ruins are considered unsafe for visitors by the Osceola Township Board. Please only observe from the road or nearby public playground and do not approach the ruins.

At this site you will see a mill stamper. These were used during the mining years to crush rock that was pulled up from the mines. The rock was then separated into poor rock, left over or waste rock, and ore, the rock that contained copper.

Figure 1: Stamper. This is a stamper that was unable to be dismantled
and is one of the few of its kind remaining in the world
Picture By: Carolyn Bolduc

Copper mining began in the 1840’s. Rock was pulled up from the mines and sent to this stamper by railcar for rough stamping. The stamper would crush the rock into smaller pieces, which would be sorted into ore, rock with copper, and poor rock, or waste rock.

The ore rock would then go through another round of pulverization to break down the pieces even further. Once the ore pieces were crushed to pebble size they were considered stamped sands. These sands were crushed rock mixed with copper. The sands would be sorted into jigs to obtain as much copper as possible. A jig is a smaller basin filled with water with a screen. The jigs job was to further separate the pieces based on the law of separation. This law states that heavier or denser pieces will settle toward the bottom while the less dense or lighter pieces would stay at the top. Copper has a higher density than the stamp sands. So gravity assisted the pieces with a heavier concentration of copper and pulled them to the bottom, while rock with little to no copper would float toward the top.

Figure 2: Stamper Pedestals Each of these pedestals once held a stamper like the one pictured in figure 1.
Picture By: Carolyn Bolduc

The last stop for the rock was the wilfley table. The table was tilted at an angle with a tray on top. The rock/water mix was poured over the table. The lighter stamp sands would wash over the table while the denser rock with copper would catch in the seams of the tray. The ore could then be collected. The stamp sands mixed with water and created slurry. This slurry was piped out and deposited directly into Torch Lake. The sands are still there along with concerns about the effect the sands have on the environment.

Figure 3: Stamp Mill Process Here is an example of the route the ore rock took to be processed.
Historic American Engineering Record. Heritage Conservation & Recreation Service.
Delineated By: Eric M. Hansen, 1978.

Logging Question:

How many pillars are still standing at the site?

  1. 3
  2. 4
  3. 8
References and Citations:

Forgrave, Mike. (2001). The Copper Country Explorer
Retrieved July 29, 2011 from: Copper Country Explorer

Google Inc. (2011). Google Earth (Version [Software].

Hansen, Eric. M. (1978). Stamp Mill Process c. 1900. (pp. 27-34). Historic Engineering Record.
Heritage Conservation & Recreation Service.

Kyburz66. (2008, June 22). Vintage Stamp Mill.
Retrieved July 29, 2011 from: YouTube

PTPath. (2009, November 26). Wilfley Table 1. Retrieved July 29, 2011 from: YouTube

Schaetzl, R. J., Darden, J. T., & Brandt, D. S. (2009). Michigan Geography and Geology. New York: Custom Publishing.