|Pirahna agate comes from the State of Parana, near Guarapuava, Brazil and appears to be closely related to what is generally called Brazilian agate. It usually has strong fortifications but often has very dark areas around a central core. (not shown in these samples)
These stones were cut as doublets with white marble used behind them to provide more reflected light. The third stone was actually made by cutting a parallel striped agate in half and mirroring it on the top and bottom.
The last stone was created using black agate as a border material. Without strong light it appears rather dark and the pattern does not show well.
All cabs cut by the author. I found that this agate tends to undercut more than most fortification agates and is somewhat hard to polish.