Table II: Percent Occurrence of Minerals in Lunar Materials All minerals listed in Table II contain appreciable amounts of oxygen, the element used in all LRU systems concepts as transfer vehicle propellant. Three of the four minerals contain silicon, the element most extensively used in SPS concept designs so far. While aluminum is a basic constituent only of plagioclase feldspars, it may also be dissolved to an appreciable extent in pyroxenes. Iron is present in ilmenite, olivine, and to a lesser extent, in pyroxenes. Depending upon the location, these four elements of interest occur in the concentration ranges shown in Table III. Other prevalent element percentages are also identified. While the concentrations of oxygen and silicon are fairly uniform in their distribution throughout the lunar surface, the concentrations of aluminum and iron vary by factors of approximately 3 to 4, each being highest in areas where the other is lowest. Aluminum is most abundant in highland locations and iron in mare regions.