How Do You Pronounce Hermetic!?

[Christian_Andersen (Christian Rosenkjaer Andersen)]

@LuckyMage

I keep seeing the books and people use "an" instead of "a" before the word Hermetic, as in "an Hermetic spell". But the name of the Greek god, Hermes, does not have a silent or un-pronounced "h" but in fact a hard, airy "h" so... I'm really confused! Are we pronouncing Hermetic as "air-metic" or "urr-metic" or something here? I can't handle it, I don't understand, help me.

This doesn't ring a bell for me. Can you quote an instance from published Ars Magica material that actually writes 'an Hermetic spell' or sow thing like it?