Old School RPG Love

I'm rediscovering the Avernum series after not having played it since 2000, and I'm loving it! I'm playing with just the basic, default party on this first-time-in-a-decade playthrough. But I've run into a number of situations in which I need to know Dispel Barrier (or use up a piercing crystal, though I know they don't work for the higher-level barriers). Problem? I feel like I've searched everywhere (including walkthroughs/faqs/etc. online) and I can't figure out how to learn even level 1 of the Dispel Barrier spell. Heck, I don't even know if it's a mage spell or a priest spell! Though I'm guessing mage. Anyway, I'm probably missing something quite obvious, but if some kind soul could set me straight, I'd be grateful.