The petrological microscope is used in the examination of thin sections of stone artifacts or pottery (ceramic petrology), in order to identify, and eventually locate, the geographical source of the rocks or minerals present. A slice, approximately 1 mm. thick, is removed from the artifact, ground until completely smooth, placed on a slide, and then the other side is ground to produce an almost transparent slice which can then be examined under the microscope. The microscope has a polarizer and an analyzer which transmits the light vibrating in one direction only; the reaction of various minerals to this type of light allows their identification; minerals refract the light in different ways because of their different crystal lattice configurations, allowing their identification.