White Rock, like all the similar formations found on Mars (and there are many, many, many) is very finely layered. Now, these layers appear to consist of interleaved beds with white layers approximately 3 meters thick separated by very thin layers of some blue/gray or blackish material. The white stuff, whatever it is, appears to literally disintegrate in the air and blow away. There is very little of its ostensible erosion product found near the formations themselves. The blue/gray/black stuff on the other hand remains relatively close to the formations, for example, as a coating on the floor of Pollack Crater and as coatings and dunes found in many other craters.

It has been argued that the white stuff and the blue/gray/black stuff is the same stuff (though no one knows what either stuff really is) just different grain size. Interesting. Probably wrong, but interesting.

Rationally, it should be obvious that White Rock and most similar formations are more or less covered with the standard Red Dust of Mars. Very little of Mars is not afflicted with more or less of this Dust.

Some of these formations are nearly indistinguishable in color and reflectance from dust covered areas nearby -- which may be why Christensen is offering his notion that White Rock is pretty nearly the same color as the red dust elsewhere. I don't know.

I would argue that there are three distinct components to all White Rock-like formations: the white stuff, whatever it is, the blue/gray/black stuff whatever it is (and it may turn out to be the more important component) and the Red Dust of Mars, and we know what that is... or do we? In some ways the Dust is as mysterious as the White Rock deposits. And one of the arguments that swirls around is that those deposits ARE dust, compressed and lithified, like shale beds. Interesting, and it could be correct.

We are unable to tell from current information just what White Rock is, and anyone who says they know is wrong. It is a mystery which cannot be solved with current resources. But the various speculations do no harm whatever. Wouldn't it be grand if White Rock was carbonate? Whoo-hoo!

Flame away.

Cheers, BRFelix