Lunar sample 72275,508.
This is sample of a friable, porous, multiply reworked feldspathic highland breccia from the Taurus-Littrow Valley area, in a range of mountains between Mare Serenetatis and Mare Tranquillitatis. It was collected by the Apollo 17 mission. The multiple episodes of reworking have caused this breccia to have within it fragments of earlier breccias.
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 one large and several small basalt fragments. The basalts are referred to in Meyer (1987) as being "pigeonite basalts", unrelated to the mare basalts and presumably older. There is also a dark breccia fragment to the lower left that itself contains smaller breccia fragments.
20X, cross polarized light
Here the texture of the basalt fragments is more clear, even if pigeonite cannot be distinguished from augite. The mafic vs. plagioclase-rich fragments in the dark breccia fragment are clearly visible by their colors.
40X, plane polarized light
Closeup of one of the pigeonite basalt fragments, showing the fractured pyroxenes with considerable dark, fine-grained material that is not all Fe-Ti oxides.
40X, cross polarized light
In cross polarized light the pyroxenes clearly enclose many of the plagioclase crystals, and the pyroxenes are strongly zoned.
40X, plane polarized light
Closeup view of the breccia fragment seen above. The matrix is very dark, unlike the largely crystalline matrix surrounding this fragment.
40X, cross polarized light
There are numerous colorful mafic mineral fragments in the dark matrix, and two large rather feldspathic fragments. The fragment close to the center is largely a single plagioclase crystal. The fragment at the top left is an annealed feldspathic breccia or melt breccia. The fragment on the far lower left is a basalt.
100X, plane polarized light
Closeup of the annealed feldspathic breccia fragment. This actually contains considerable mafic mineral content, ~40%, most of which has rather low birefringence. I interpret this to be a fine-grained norite breccia that has annealed to smooth grain boundaries.
100X, cross polarized light
In cross polarized light the partially annealed texture is more visible, with small scale development of triple junction grain boundaries.
200X, reflected light
Quenched glass fragment with feathery and radiating plagioclase and pyroxene crystals.
200X, reflected light
Interstitial material between pyroxenes and lath-shaped plagioclase crystals in one of the pigeonite basalt fragments. Dark grays are silicates. Medium pinkish-gray is ilmenite. Creamy brown is troilite. Bright white specks are native iron. This interstitial material may also contain alkali feldspar and silica.
100X, reflected light
Spongy iron grains possibly resulting from in situ reduction of silicate iron.