I am prone to believe that the old cultures also used the crystals for other purposes ( energy or ... idk) other than just healing and personal enlightenment. Something is pretty much off about how much relevance they were giving to the materials that posses a certain inner structure and allegedly not knowing what that structure is.
That's true, Crystals were used for varied purpose in the olden days in every culture and a lot of myths also created around it, but I personally use them in my healing therapies and find a lot of help.