Magnetite is a black iron-bearing mineral that has its own magnetic charge. Because it’s denser than the rest of the sand in the dunes, it often separates out through the actions of wind or water. On dune ridges, wind blows away the lighter sand, leaving black streaks. These can eventually form into layers of black sand that unevenly erode in the wind, forming black swirls and patterns. The braided channels of Medano Creek can also leave curved patterns of black sand in the creek bed. While all magnetite has some magnetic charge, scientists have determined that strongly-charged magnetite on the surface of the Earth is charged by lightning strikes (Wasilewski and Kletetschka, 1999). Magnetite in the dunes has its own relatively strong magnetic charge. A large patch of magnetite can spin your compass around! Birds, salmon, and some other migrating animals may use a biologically-derived form of magnetite, synthesized within their bodies as a part of a system used to navigate using Earth's magnetic field (Wiltschko 2021 and others). You can pick up and play with magnetite sand using a commercial magnet or a piece of magnetite, but please leave it in the park so it can also be enjoyed by future generations. All resources at Great Sand Dunes are protected by federal law. |
Last updated: November 7, 2024