This is one of those things that one would assume to be self-evident, given that masonry is more dense than water, but it is incorrect by a large margin.
You have to go by the "specific heat" of the material, and water's specific heat is dramatically more than masonry (about a 5:1 ratio). Don't believe me? Ask the masonry industry:
http://www.cmacn.org/energy/basics/mat_sh.htm
I'm not trying to be snippy, but it _is_ essential to tie discussions and advocacy back to physics, not supposition.
Water's physical characteristics, specifically in regard to heat retention and heat-transfer, would be considered truly extraordinary in comparison to nearly all other materials (except for really exotic phase change materials), except we're all so used to having the stuff fall out of the sky that we don't stop to realize that it has these unique properties.