It might be soft.

It might be poorly cemented and full of small holes (porosity).

There seem to be harder portions withing the micro views, or at least areas that seem to "smear" slightly, like a clay might. Or the soft stuff is smearing onto harder surfaces. Or same stuff wihtout open intersticial areas.

Wish I could spit on it. Really. After I smash a rock with my trusty hammer, I either spit on it or drop some water from my water bottle on it. If I am looking at rock core, I have a spray bottle at hand at all times. You have to remove the dust from grinding and rocks show more when wet. But we can't do that with the rover for obvious reasons. A little compressed air would help.

I'll spit on the floor instead.

What was that strange branching thing in the other images?

So cool.