Where I Found It
south-central Indiana near Shelbyville.
How I Found It
A land owner brought it to me for identification, along with a collection of similar round concretions. He invited me to his property, where it became evident that the concretion was one of several scattered in crushed limestone brought in to repair his driveway. So it is likely from a local quarry. All were masses of iron sulfide, or pyrite, and as happens for this mineral, the owner hoped it might be valuable. For my efforts to explain its origin, he gave me one of the nicest egg-shaped examples.
- Pyrite is a common and often attractive mineral, but usually it occurs in cubic crystals or aggregates of cubes. Less common is this concretion form, which might have formed in limey seafloor mud, before it lithified to limestone. I keep it to display in a collection of stone eggs, most of which are cut and polished to their shape. Not this one!