Spheres

If it is spherical, then it is not a meteorite. All of the photos on this page were sent to me by people who asked if the objects were meteorites. There are many natural processes on Earth that lead to near-spherical rocks. I suspect, however, that several of the objects depicted here are man made.

Dark, spherical rocks. Some might be largely hematite or possibly pyrite. The blackest ones might be basalts.

A variety of spherical rocks.

If it has stripes, then it is not a meteorite. See also Layers and Stripes.

Many people send me photos of spherical rocks. The one next to the basketball may be a “cannonball concretion.”

These reddish rocks may all be hematite concretions or coatings.

The mineral pyrite is the most common form of iron sulfide in nature. It forms cubic crystals. Small cubes sometimes aggregate into spheres to form a pyrite concretions. Pyrite concretions catch people’s attention because they are round and dense. In some of the photos, if you look hard, you can see the cube corners sticking out. On the reddish ones the iron sulfide has oxidized to the iron oxide hematite. If you saw or break them in two, you can see the metal-like pyrite. 

Some spherical pyrite nodules radiate from the center and catch one’s attention when broken open.

These things are called septarian nodules or septarian concretions. The one on the lower left is filled with calcite. I suspect that it was purchased from a dealer because it appears to be polished. This type of septarian nodule is  readily available on the Internet. The other three appear to consist mainly of hematite. I believe that this morphology is also “septarian.” (Somebody correct me if I am wrong. I’m a lunar geochemist, not a terrestrial sedimentary geologist!)


OK. You’ve gotten this far, so I’ll back off a bit. The photos below are both of spheroidal meteorites – not perfect spheres, but spheroidal. This as about as spheroidal as meteorites are found.

Both of these photos were sent to me. The meteorite on the left appears fresh, with a glassy fusion crust and contraction cracks. The one on the right is quite weathered, but fusion crust still remains on about 80% of the surface that we can see.