Why this rock is probably not a meteorite:

1) It's too spherical. Meteorites are never this speherical because there is no mechanism to make spherical rocks on asteroids or the Moon. (We don't know yet whether any rocks on Mars are speherical.)

2) Up close the rock does appear to have a rind, and it's smoother than where the rind is missing on top. However, the rind is too thick to be a meteorite fusion crust, and it really doesn't look glassy like a fusion crust. In meteorites, the fusion crust is almost always darker than the inside of the meteorite. The inside of this rock, where the rind is missing, is very dark.

3) The rock is dense, but not magnetic.  It does not contain metal. Up close, there are a few crystals of calcite exposed. Calcite doesn't occur in meteorites. The bulk of the rock is so fine grained that individual crystals cannot be seen with the naked eye. Meteorites that do not contain metal will have visible mineral crystals or rock fragments on the inside.
What is it?

This strange looking, 42-pound object is called a coal ball. Coal balls are not made of coal, but they are found only in coal beds. Coal balls are ancient masses of peat that has been cemented by calcium or magnesium carbonate. Coal balls are often rich in fossils.

This rock was found in a shop in Indiana. Coal balls are common in coal deposits of Indiana and Illinois.

Here is a photo of the coal ball pictured above along with another coal ball that is in our department collection of rocks and minerals.


Prepared by:

Randy L. Korotev

Department of Earth and Planetary Sciences
Washington University in St. Louis

Please don't contact me about the meteorite you think you’ve found until you read this and this.