AGuest, your story continues to facinate me.
Glad to oblige, dear Sab (peace to you!).
In what time period did you conduct your ancient tribal research?
In the time period that came before the time period that came just after the time period... that brown triangles were popular (due to their rarity), dear one. Which was sometime between the time that their carriers exchanged eating dirt for eating wormwood... and your finding this specimen. Some of my colleagues refer to it as the "Age of Compost"... but that's really inaccurate because it describes the transition in reverse...
Hope that helps... and a hefty piece of mafic to you!
SA, on her own...