Although no one knows for sure how these agates formed, there are at least two theories. Some believe that polyhedroid agates are pseudomorph replacements of other, more angular crystals. Another hypothesis is that they formed in spaces between other crystals, perhaps calcite. Unlike the rest of the Brazilian agates found in the southern part of the country, these unusual agates are found at a single site in the northern state of Paraiba. There has been no mining of polyhedroids in recent years. Most were mined during the 1970s.

4.6 x 4.6 x 2.75 inches