There's only one safe way to control if it's sapphire or not : buy one of these diamond testers on ebay. They're not that expensive.
The water drop test is one good clue but not 100% reliable : I have a PAM111 with sapphire crystal and the water drop will spread on it.
It's possible to remove the AR from mineral, but I would leave this to specialists like FineDD.
Synthetic sapphire is one of these funny description from the Microsoft brothers (The Cartel) to mislead buyers. This is one of the many examples which explain why they are not trusted dealers on RWI.
Which I can't understand is why the rep factories insist in supplying these horrible blue AR, whereas we have seen there are many other possibilities, for cheap. Look at the Sinn AR, the cheapest have an excellent transparent slightly purplish AR, and they cost not more than a PAM)