Most of the rock in the major mountains (Pukhansan; Soraksan. . .) is granite, but there is limestone, gneiss, basalt, sedimentary, conglomerate etc throughout the country. When possible, I try to include rock type in posts. Hopefully this semester I'll have a class of natural science majors (didn't last sem) and once again offer a bonus point for IDing my samples

I took geology 20 years ago to fulfill science requirements, but it wasn't my best subject. Maybe there's a geologist out there? (Sometimes I find this info on websites or books, sometimes in Korean or English, but offhand I don't know of a primary source for it in English.)