I'll do a "porous" test on these .. I'll take dry weight, and then let it soak in water overnight and take wet weight. I'll do the same with the regular ancient reef rock (CaribSea SouthSeas) that we carry and will post the results in the near future.
"Since our rock is created so porous and lightweight pound for pound you will actually get more rock in your tank, an important consideration when you pay by the pound."
I haven't compared it to our other rock (CaribSea SouthSeas) yet, but will do that soon.
Regarding weight of the archways -- they were all around 4lbs each. Weight for pieces is in the title in the flickr link that I posted.