Treasure/Banded Iron Formation

Red hematiteWe collected this sample of banded iron formation (BIF) from the Upper Peninsula of Michigan. It’s 2 billion years old. This is the rock that is the evidence for the first oxygen in our atmosphere. Algal bacteria began giving off oxygen that bonded with free iron in the ocean, like rust, and settled to the seabed. Then this sample got deformed into a nice fold. Now, almost all the world’s steel is produced from BIF. It’s a fabulous tool for teaching about earth history.

The red is hematite. The shiny black is magnetite. Then, some of the real bright red is jasper. Even though I’ve been studying rocks for 40 years, I still say, some of them are just doggone beautiful.

When we went on a field trip this fall, to the tip of the UP, we drove an hour out of our way so students could collect their own samples. They make fabulous Christmas presents. When students give them away, it gives them a chance to say, “And by the way, let me tell you about this. This rock is 2 billion years old and, when it formed … .”


Nov. 10, 2017