Polarized light microscopes have been used in classical earth science studies for the last 100 years. Since then a lot of progress has been made to increase the user friendliness, ergonomy, and optical performance of such microscopes.
Still, one thing has not changed: Classical polarized light (compound) microscopes can only be used for prepared samples, because the working distance they offer is insufficient for whole samples. This means that thicker and bigger geological samples have to be sectioned and polished to fit under the limited working distance of a compound microscope.