Wow Indeed !
Exactly the sorts of questions everyone is wrestling with.
Note also the comments from the NY times this morning, that the Mini-TES results didn't show sandstone, carbonate, silicates, or anything else expected. Again, the surface layers may be radiation damaged and not showing up right, or they could be real wierd shit (good geological terminology there)!
It'll be real good to see what's inside the rocks, and whether it gives better TES response, plus the Mossbauer spectra for iron minerals.
On Earth, pale red rocks would be interesting. On Mars they're fascinating !
My guess is volcanic ash, but I could be wildly wrong...