https://www.msn.com/en-us/news/world/secret-of-ancient-maya-blue-pigment-revealed-from-cracks-and-clues-on-a-dozen-bowls-from-chich%C3%A9n-itz%C3%A1/ar-AA1EfJpq

Maya blue is a highly unusual pigment because it is a mix of organic indigo and an inorganic clay mineral called palygorskite.  

Echoing the color of an azure sky, the indelible pigment was used to accentuate everything from ceramics to human sacrifices in the Late Preclassic period (300 B.C. to A.D. 300).

A team of researchers led by Dean Arnold, an adjunct curator of anthropology at the Field Museum in Chicago, determined that the key to Maya blue was actually a sacred incense called copal.
By heating the mixture of indigo, copal and palygorskite over a fire, the Maya produced the unique pigment, he reported at the time.

www.plutorules.com/page-111-space-rocks.html

This help’s us understand the composition of components in/on solar system bodies.

Dips in the observed light spectrum, also known as, lines of absorption occur as gasses absorb energy from light at specific points along the light spectrum.

These dips or darkened zones (lines of absorption) leave a finger print which identify elements and compounds.

In this image the dark absorption bands appear as lines of emission which occur as the result of emitted not reflected (absorbed) light.

 

 

 

Lines of absorption

thomasmansencal.blogspot.com/2014/07/a-homemade-spectroscope.html