it seems to be that the sapphire ring should be in a mueseum.
given how Diana died, Kate is, in my eyes, tastelessly wearing her ring.
no, anon, the pyramids at Giza are made of Limestone blocks, not concrete.
Concrete wasn't invented till much later.
there is a theory that the stones were made in 'forms'. This theory is not accepted by many scientists, so the source wikipedia references claims.
one thing that would say 'no, it wasn't made with a very ancient type of limestone concrete' is that all the stones of a level of the pyramid are at the same height, but the different levels are all different heights.
why would they building then not have levels all at the same height if they were easily formed. The manufacturing of them would have allowed for far more precise stone sizes, and a standard sized stone.
and thus most feel that the stone were quarried near by and brought over.
this also make sense because otherwise the stone would have had to have been ground up and then reformed as concrete, using a lot of water, and that's a dessert, even though there is a river there.
anyway, theories vary. And perhaps there is some concrete 'at the entrances' as you say.
https://en.wikipedia.org/wiki/Egyptian_pyramid_construction_techniques