Magnification key:

200x = 0.80 mm image width

500x = 0.32 mm image width


Sample 12002,320

 

200X, reflected light.

 

Chromite occurs in this sample, suggesting it is one of the more primitive lavas. In olivine, chromite is pristine. In the matrix, chromite is overgrown (partially replaced by?) ulvospinel. In this image, the dark gray shades are silicates. The medium gray laths are ilmenite, the light gray in the center of grains is chromite, the pinkish-brown overgrowths on the chromite are ulvospinel, the creamy brown bits are troilite, and the bright white grains are iron. Notice how the chromite grain embedded in olivine (right) is euhedral and not overgrown with ulvospinel.



Sample 12002,320

 

500X, reflected light.

 

Closeup of a chromite overgrown (partially replaced?) by ulvospinel. Colors are as above. Notice the large bright white native iron grain, and the small specks of iron in the triangular troilite grain toward the lower right.



Sample 12005,39

 

500X, reflected light.

 

This is a crystal of ulvospinel (pinkish region). From the ulvospinel have exsolved thin lamellae of ilmenite (brighter) and spinel (medium-gray). The adjacent olivine crystal is dark gray.



Sample 12005,39

 

500X, reflected light.

 

Trapped interstitial melt that quenched to a fine network of skeletal olivine and pyroxene (medium gray) and ilmenite (white). Darker gray regions are plagioclase and possibly other silica-rich minerals, and residual glass.



Sample 14305,176

 

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.



Sample 70017,113

 

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.



Sample 72275,508

 

200X, reflected light.

 

Quenched glass fragment with feathery and radiating plagioclase and pyroxene crystals.



Sample 72275,508

 

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.



Sample 72275,508

 

100X, reflected light.

 

Spongy iron grains possibly resulting from in situ reduction of silicate iron.



Sample 74220,355

 

500X, reflected light.

 

This is an orange sphere in which numerous olivine blades nucleated and grew. In this image, the darkest gray material around the margins is epoxy. In the sphere, the darker gray material is glass, the lighter gray blades are olivine, and the bright white plates and specks are ilmenite. The parallel growth of the olivine blades in most samples is remarkable.