Geology of the Moon the Moon. Lunar rocks are in large part made of the same common rock forming minerals as found on Earth, such as olivine, pyroxene, and plagioclase feldspar (anorthosite). Plagioclase feldspar is mostly found in the lunar crust, whereas pyroxene and olivine are typically seen in the lunar mantle. The mineral ilmenite is highly abundant in some mare basalts, and a new mineral named armalcolite (named for "Arm"strong, "Al"drin, and "Col"lins, the three members of the Apollo 11 crew) was first discovered in the lunar samples. The maria are composed predominantly of basalt, whereas the highland regions are iron-poor and composed
Silicate minerals Silicate minerals Silicate minerals are rock-forming minerals with predominantly silicate anions. They are the largest and most important class of rock-forming minerals and make up approximately 90 percent of the Earth's crust. In mineralogy, silica, or silicon dioxide SiO, which corresponds to "x"=2 in the general formula, is usually considered a silicate mineral—even though its silicate "anion" has no negative charge and it has no cations. Silica is found in nature as the mineral quartz, and its polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes