Ted
Where is the quarry for the dark grey/black limestone used to reconstruct the castles and for new 'traditional' stone structures? I have even seen pavers and building facing cut from the same material.
Akane
I think Japan had a lot of different quarries all over the country providing stones for the castles and other structures. They name the stone after the quarry so it’s difficult to know exactly which kind of stone it is geologically speaking, and I’m not sure what kind of stone you’re talking about.
Anyway, here’s a website for a granite quarry on Shodoshima island which provided stones for the Osaka castle. http://www.japanvisitor.com/japan-city-guides/castle-stones
And you can visit the Oya stone quarry museum which provided stones for houses, temples, etc. in the area. https://planetyze.com/en/japan/tochigi/oya-history-museum