[John H K]

Yep, seems water had to have been involved.

So what do you think of the closeups of the outcrop rocks? That's some REALLY fine foliation.

Now that the pics are closer they look like they MIGHT be "crumbly"...I'm curious if they're really hard or if they'll crumble when the arm is put on them.

[doodad]

Obviously they are weathering differentially as the spheres are being left as the matrix breaks down. I also noticed that the spheres are in most cases larger than the layer they occupy, which would also indicate that they "grew." The only other thing I can think of would be infilling of gas bubbles by a solution. However, they mentioned that large amounts of olivine was present which does not exist with quartz, so they are not siliceous unless a long time gap occured and a change in source materials provided the silica.