Lunar sample 14305.
This is polymict, which is an impact breccia that incorporates fragments from different lithologies. It consists of a very fine-grained crystalline matrix and fragments ranging from anorthosite to mare basalt. Many of the fragments are themselves breccias. This sample was collected by the Apollo 14 mission to the Fra Mauro crater, on the northeastern margin of Mare Nubium. The material represents part of the Mare Imbrium ejecta blanket. Rocks of this type from the Apollo 14 site have been dated at ~3.82 Ga.
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 low magnification view shows a dark matrix in which are set a variety of crystal fragments and lithic fragments including breccias. The large light-colored fragment on the right is shocked anorthosite. The large grain to the left of center is a breccia clast, as is a smaller fragment closer to the lower left corner.
20X, cross polarized light.
The fragmental nature of the breccia clasts is more obvious here. The two clasts on the left are quite feldspathic.
40X, plane polarized light.
Basalt fragment. Notice how the edges are rather fuzzy and not sharp. The heating event that melted and permitted crystallization of the matrix also permitted partial assimilation of some of the clasts, making their margins less clear.
40X, cross polarized light.
The two grains at the very top of this basalt clast are colorless and have high birefringence, and are probably olivine.
100X, plane polarized light.
This is a small fragment of a probably gabbroic rock. It may represent only a few highly shocked plagioclase and pyroxene crystals.
100X, cross polarized light.
Here the fragmental nature of this fragment is obvious.
100X, plane polarized light.
This is an unusual plagioclase fragment That appears to have undergone considerable shock deformation.
100X, cross polarized light.
The unusual texture of this plagioclase-rich grain is indicative to me of shock-induced deformation twinning.
200X, reflected light.
Quenched glass fragment with lath-shaped dark-gray plagioclase, lighter gray pyroxene, bright white specs of iron, and tiny light brown crystals of ilmenite. Much of the matrix of this breccia thin section looks like the finer-grained matrix of this fragment.