"The interest in Maya blue stems from the fact that it is a very durable pigment -- more durable than most natural dyes and pigments. It also stems from the fact it wasn't immediately obvious how it was made and what the key ingredients were."
The pigment resists age, acid, weathering, biodegradation and modern chemical solvents. Previous research had identified two ingredients as extract from the leaves of the indigo plant and an unusual white clay mineral called palygorskite.
These researchers did microscopic analysis on material found in a three-footed pottery bowl in the museum's collection dating from A.D. 1400 that had been used as an incense burner.
I'd thought someone figured out Maya blue a while ago, but I guess not. The blue goo at the bottom of the cenote is way cool. Feinman was one of my perfessers at the U of Wisconsin.