Thanks, I'll check if I've got a comparator IC lying around in DIP format and breadboard it. With luck I might even have a comparator with the same pinout as the op amps I've breadboarded this with before, swapping back and forth will make differences in behavious very clear, if the comparator version will behave at all.
Why not a crystal? This is for an application where I'm using colpitts frequency as a meaure of inductance and eddy current sensing.