For the mineral pile located behind the Interpretive Center, next to the far side of the parking lot.
We bring in truck loads of rock from the fluorite mines of Hardin County, Illinois every year. Visitors dig for minerals. The piles are turned several times each year. They reveal their secrets after it rains.
What can I find in this pile?
There are four common minerals. They may be crystals with distinct faces, crystalline (intergrown, without distinct forms), or massive.
Fluorite…is a crystalline mineral often purple and yellow color that is composed of calcium and fluorine. It is an important mineral used in U.S. industry to make steel, aluminium, and a zillion chemicals! If it sounds familiar, perhaps you have used toothpaste with fluoride in it. Fluoride comes from fluorite!
Calcite…is a white crystalline mineral composed of the same material as limestone (calcium). It is commonly found a crystal fragments in the shape of a rhombohedron (it has two diagonal edges instead of square ones). This mineral is used to make lime and other chemicals.
Barite…is a heavy white mineral made of barium that, at first glance, looks like a lump of chalk. The crystals are usually intergrown and very tiny, so it looks like a solid white rock. The density gives it away – it is very heavy for its size. Unlike calcite, it doesn’t fizz with vinegar. Barite is used in drilling for oil and in several medicines.
Sphalerite…is the brown to reddish-brown crystalline material composed of zinc. It is very sparkly, reflecting light easily. Crystals can be the size of a grain of sand or as big as your thumb. This mineral is used to make a lot of different things, from poison ivy anti-itch creme to car batteries!
Many specimens on the collecting pile are combinations of more than one mineral.
Here are some examples: