Prior to my visit to Rondi’s lab, I thought Jade was Jade. Ah, there is no boundary to my ignorance.
“Jade” is a common name shared by two unrelated mineral forms. There’s nephrite Jade (think most traditional Chinese carvings) which can be found all throughout Russia and China. Then there’s Jadeite which is exceedingly rare and found in Guatemala and Burma.
For years, Dr. George Harlow, Curator in Earth and Planetary Sciences at AMNH has been studying jadeite from the Guatemala Suture Zone, the boundary between the North American and Caribbean tectonic plates. This former subduction zone marks places on the earth where two plates meet and collide. Oceanic plates (most of the Caribbean plate) are made of denser rock than that of the continental crust and sink beneath the other. Water carried down with oceanic crust is heated and hydrates certain rocks to form serpentine minerals. Jadeite is formed by the passing of this fluid through and over parent rocks. (NOTE: Add Youtube video of George https://www.youtube.com/watch?v=TWofncaF2Ds)
Jadeite most commonly takes a hue of green; however, may include a variety of colors including pink, lavender and blue (Note: Add a picture of an Olmec head made of jadeite). Jadeite is fairly well studied, but something known as black jade that is found in close proximity to jadeite. Scientists don’t know from what parent rock it was derived or what that transformation process looked like. Knowing how a mineral forms can unlock clues to the evolution of the earth’s crust. Therefore black jade is like finding a blank page in the Earth’s history book. Khakima, Carlos, Rosa and Rondi are attempting to fill in the blanks studying black jade of the Guatemala Suture Zone
The process of understanding how black jade formed requires careful observation with a high powered petrographic microscope. The team are scanning thin slices of these rocks to find evidence of the original rock prior to it being altered by and recrystallized from fluids: they are looking for sections in the rocks without small fluid droplets trapped inside minerals, and for chemical zoning (areas with evidence of the mineral growth) to map the changes that black jade experienced from its parent rock to final form.