No more stone pits?

[Andergaster]

I am in the early Middle Ages and can no longer build stone pits. I demolished the existing ones to test them. It still doesn't work.
Can anyone tell me why?

[mathemagician]

They are deprecated by mines. Meaning you should be able to build mines instead.

[Andergaster]

ah okay, thanks. yes I don't have researched engineering.
I wouldn't have thought that stone pits can no longer be built even though you don't have the next tech.