1. adj. [Geology]
Pertaining to petrography, the examination of rocks in thin section. Rock samples can be glued to a glass slide and the rock ground to 0.03-mm thickness to enable observing mineralogy and texture using a microscope. (A petrographic microscope is a transmitted-light polarizing microscope.) Samples of sedimentary rock can be impregnated with blue epoxy to highlight porosity.