Lunar sample 70017.
This high-Ti basalt is typical of the older mare lavas. High-Ti lavas (9 to 13% TiO2) are generally confined to the period 3.85 to 3.55 Ga, whereas the low-Ti lavas (1 to 5% TiO2) are most common in the period 3.45-3.15 Ga (Meyer, 1987). The high-Ti basalts are thought to have been derived from olivine-pyroxene-ilmenite cumulates that formed during crystallization of the magma ocean. This basalt was collected from the Taurus-Littrow Valley area, in a range of mountains between Mare Serenetatis and Mare Tranquillitatis, by the Apollo 17 mission. This sample was dated at ~3.70 Ga.
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 contains abundant pyroxene, plagioclase, and Fe-Ti oxides that include ilmenite, ulvospinel, and armalcolite. There is minor olivine.
20X, cross polarized light
This shows large pyroxene and plagioclase crystals, with opaques scattered throughout. Pyroxenes are color zoned and generally have augite cores and pigeonite rims.
40X, plane polarized light
The grain in the center is olivine, which is euhedral against plagioclase but not against pyroxene, typical in this sample. A few other colorless olivine grains are visible, though they are identified better in the image below.
40X, cross polarized light
Olivine crystals can be seen at the far left center (orange), center (yellow), and several small crystals toward the lower right (pale pink).
100X, plane polarized light
Closeup of the principal minerals, including euhedral olivine in plagioclase (center) and anhedral olivine in augite (center of the lower left quadrant).
100X, cross polarized light
The extent of the olivine crystals is more easily seen here.
500X, reflected light
In the center is a rather large grain of troilite, with unmixed iron droplets. The pinkish-gray minerals to the left and right are ulvospinel, containing ilmenite exsolution lamellae.