Lunar sample 12002,320.
This highly brecciated lunar anorthosite was collected by the Apollo 16 mission to the lunar highlands southwest of Mare Tranquillitatis. It has been dated at 4.44 Ga, and so is one of the oldest lunar rocks analyzed.
Magnification key 20x = 8 mm image width 40x = 4 mm image width 100x = 1.6 mm image width 200x = 0.8 mm image width 400x = 0.4 mm image width 500x = 0.32 mm image width |
20X, plane polarized light.
This rock is a highlands anorthosite, presumably a cumulate that formed as part of the early lunar crust. This rock is really a lithified anorthosite breccia or cataclastite. It contains ~98% plagioclase of An95 to An97. It apparently contains fragments from several different anorthosite compositions, and is not derived from a single homogeneous body. Pyroxenes include augite and orthopyroxene, and olivine is rare.
20X, cross polarized light.
In this photo you can see a fractured and faulted plagioclase crystal (center) and numerous other deformed, faulted, and polygonized grains. Notice that all grain sizes exist, from large to very small.
100X, plane polarized light.
Closeup of the central faulted grain in the photos above. Small aligned pyroxene rods occur in this plagioclase, probably a primary igneous feature. Numerous small pyroxene grains are scattered about.
100X, plane polarized light.
Offset twin boundaries are clearly visible in this grain. Note the very small grain size of the matrix.