Lunar Basalt

Photomicrographs of Lunar Basalt
photo by J. Gerencher using a petrographic Microscope

This thin section of lunar basalt, sample 70017, was photographed using plane-polarized light (upper photograph) and also using cross-polarized light (lower photograph) with a petrographic microscope at Moravian College.  The lunar sample was on loan from NASA and has since been returned.  Three minerals are evident.  The minerals which are opaque (black) on both views are ilmenite, which is an iron/titanium oxide.  The minerals which are white to gray on both views are plagioclase feldspars.  The minerals which have a high relief in the upper view and exhibit various colors in the lower view are pyroxenes.  The bright colors in the lower view are interference colors which result when the sample is viewed between cross-polarizing filters. 

This lunar basalt is very similar to Earth basalts in both the compositions of the constituent minerals and texture of the rock.   The petrographic microscope uses both plane- and cross-polarized light to permit the identification of minerals which make up the rocks around us, as well as those from other worlds.