Indiana Dunes National Lakeshore on a beautiful day! Read below about the black particles that line the beach.
Copyright © 2018 Loralei U. Brown
“It may makes sense that beachgoers assume the dark grains are pollution from the steel mills that dot the South Share. But the tiny particles are actually naturally occurring and the product of the multiple glaciers that dug out the Great Lakes long before any industry showed up on the scene, according to Erin Argyilan, geoscience professor at Indiana University Northwest in Gary.
The dark grains are a combination of magnetite and ilmenite, which are heavy minerals and iron ores, she said. They are from large rocks up north, which were pulverized and carried south to the local beaches by the glaciers.
They are among 20 minerals identified at least as far back as 1931 by Francis Pettijohn, a one-time professor at the University of Chicago.”
This statement was passed on to me by a fellow photog.