Prospecting

Title: Chart of Test Pits
Type: Diagram
Date: 1892
Source: Minnesota Historical Society

Description: These are diagrams of some test pits that were dug from a mine on the Iron Range, near Hibbing.

Activities:

1. Which layers do all thee test pits have in common?
   
   
   
   
   Answer: They all have glacial drift at the top and a layer of paint rock just below the glacial drift.
2. What do the numbers down the center of each test pit graphic stand for?
   
   
   
   
   Answer: These are the number of feet below surface level at which each new layer began.
3. Why were these pits not dug deeper?
   
   
   
   
   Answer: All three of the pits were stopped when the diggers hit water. Once water was hit, the pit would have to be drained with a pump, or the prospector would switch to drilling in order to go deeper.
4. Would these ore deposits best be mined by an open-pit mine, or by an underground one?
   
   
   
   
   Answer: Since the actual ore deposits don't show up in these pits until about 50 feet of digging, this area would be best mined with an underground mine. Fifty feet of rock and dirt would be too much to remove for an open-pit mine.