Stones
All the Stones are magical and physical attempts to copy the Zero Stone. They allow a tower to focus its energy to mold creation. Many times the Stones borrowed from Oblivion and attached the power to the Tower. The builder of the Towers “took” from Oblivion because it is difficult to bypass it in an attempt to tap the Aetherius. It has been done, but the cost was high. In comparison, it is much easier to tap into the power of Oblivion.
The Stones collected “creatia” that came into the Void from Aetherius.
The Daedric Realms were formed in the same way, using extra energy from the Aetherius to build each realm. The realms of Oblivion are more “capricious” then the Towers on Mundus. . . Sometimes!
The Altmer tired to emulate “the will of Anuiel” [Order?]. The Chimer rebelled against aedric ordering and measures and followed Veloth to Red Mountain to “the Stone that is not a Stone that is” [Heart of Lorkhan]. The worst Tower, Walk-Brass, went beyond creation into dis-creation. The Numidium posses a threat to the Emperor [Empire], but it is a small part of a larger evil.
The White-Gold Tower has a stone called Chim-el Adabal, AKA the Amulet of Kings
From here http://www.imperial-library.info/content/facts-and-opinions-nu-hatta-intercept
The orichalc tower is mentioned in there as well
In greek orichalc was and still is sometimes used as another name for bronze (or brass)
Brass and bronze are similar which is confusing for TES as there is already a brass tower (the anumidium)
Brass is any alloy of copper and zinc Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminum, or silicon