I am writing a paper that describes nuclear reactions that take place in the earth's crust leading to the formation of volatile gases. In several places, I need to distinguish between things that happen in solid rock vs in microscopic gas pockets that can form in pores and between grain boundaries. I would like to introduce a technical term to denote the former since I find myself repeating the verbose distinction several times.
How best to render "in rock" in Latin? My dictionary suggests "in saxo" and "in scopulo", but those both seem to suggest a rocky outcropping or a piece of rock, and I'm hoping to convey something more like "in solid bedrock". "In silico" would probably work, except that it already has a very different technical meaning in this field (referring to simulations "on silicon" as opposed to experiment).