Cappadocia, Caesarea AE 15mm. Dated Regnal Year 3 of Trajan = 100 AD. Turreted bust of Tyche right / E-T either side of pyramidal form, G in ex.
This coin’s reverse is particularly strange and interesting. The triangular form has not yet been convincingly identified, leaving us with two theories and no certainty. The pyramidal form has been called a baetyl, or a sacred stone by some, comparable to the stone of Magna Mater or the famous black rock that was worshiped by the Roman emperor Elagabalus, though it is not known that such a stone existed at Caesarea beyond the evidence of coins. The other prominent theory is that the pyramid is actually a stylized version of nearby Mount Argaeus (Erciyes), the highest mountain in central Anatolia. There are no other instances that I know of that show a mountain in this strange way.
These coins, with their strange reverse, seem to have been popular in the reign of Trajan, but become rarer later, appearing only once under Antoninus Pius before disappearing again.
If the coin does show a baetyl, in most cases these stones were meteorites, and were worshiped as containing a life of their own. The last of the great ancient stones that still is prized is the black stone of mecca, which is believed to date back to the time of Adam and Eve and was set in place by the Prophet Muhammad in 605 CE.