Illinois (left) and Arkansas (right)
All 8 of these concretions were found in the country of Georgia.
Idaho (left) and somewhere in the U.S. (right)
Missouri (left) and Morocco (right)
These 4 are from China.
All of these are all from China.
I found this photo on e-bay. The rock was offered for sale as “0.8 lb Meteorite Specimen from Nandan, China!” The “Buy It Now” price was $295. It looks like a hematite concretion to me. Many hematite concretions start out as masses of cubic pyrite (iron sulfide) crystals that oxidize to hematite (iron oxide). That’s what this one looks.
From somewhere in Europe
England (left) and Australia (right)
Peru (left, botryoidal) and Massachusetts (right)
Four from Peru
left: somewhere in the U.S.; right: Texas
Hematite coatings and crusts
Here are two views of a thick rind of hematite on a rock (sawn face on right).
A most excellent example of a hematite coating precipitataed onto a host rock. Thanks, Daniel.
“Found in the sea” (left) and somewhere (right)
More pyrite oxidized to hematite
Two views of hematite nodule from Arizona