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NWA 5000 Lunar Melt Veins

I was given thirteen NWA 5000 Lunar (feldspathic breccia) thin sections to photograph. Each section has melt rock that merits attention. In some it appears as small puddles but in most it appears as veins, some traversing the full width of the sample. Of course thin sections are just that – thin (virtually two dimensional) sections taken from a three dimensional rock. What we call veins are portions cut from sheets of melt within the rock and the puddles are likely portions of tubular passages within the rock through which melt was forced.

The melt rock solidified before it could crystallize so it is glass. Consequently it appears black when viewed in cross-polarized light. I took these photos with the top and bottom polarizing filters only partially crossed – and by different amounts. We get the feeling that the glass had been flowing when it froze. Visual clues are alignments of included solids, alignments of bubbles, deformed bubbles and the appearance of ripples which are probably density differences in the glass.

In some images we sense a distinct direction of flow. Still, we should remember that in the three dimensional world there also might have been a flow vector, large or small, away from the viewer or toward him in each case.













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