[Openurmind]

Actually taking another look at building materials might be in order here. Pretty sure they used both. And the Granite they used has very high piezo electric qualities. While the Limestone has insulating qualities. By design for some reason?

[SoCal Pubbie]

I'm always amused by folks who say the ancients had to have had either esoteric advanced knowledge that was subsequently lost to time, or help from ancient astronauts to build their great structures, because it would have been too difficult to do so by modern standards. Like the old line about no modern crane could lift the blocks of the pyramids. What that shows is that modern engineering builds large structures using components that weigh much less. There's no need for such a crane.

Here's one quick link on how they cut granite:

https://sciencing.com/granite-quarried-ancient-egypt-6032.html

Perhaps they used diamonds, which are harder than granite:

http://www.theglobaleducationproject.org/egypt/articles/petrie.php

Or maybe they used sand:

https://www.pbs.org/wgbh/nova/lostempires/obelisk/cutting.html

The exact technique may remain undetermined for now, but hardly mysterious.

As for gold on the statues, they weren't plated, they were gilded. Much like gold leaf, or the gold inlay on fancy medieval suits of armor. No electric current needed.

Here's a detailed piece on ancient Egyptian goldsmithing:

https://core.ac.uk/download/pdf/81790937.pdf