At high pressures, fluorine-free topaz is stable: Topaz-OH. It's likely present only on recent Earth in our solar system: water, aluminous sediments (shales; pelites) from continental crust and cold subduction zones are all required.

Given these, Topaz-OH can potentially transport water into the mantle transition zone (where it's stored in #ringwoodite ) Figure from Huang et al (2020).

#MinCup24 #Topaz #subduction #mantle #DeepWaterCycle