"Thus the Q of
the -crystal- is not a function of the mode of operation."
------------------------------

Wes,

If you're speaking of the Q of the crystal's inherent series resonance, then
you're right. However, most crystal oscillator circuits that we typically
see in common use operate in the parallel resonant mode, which isn't a
crystal resonance at all. It's the frequency at which the crystal's net
inductive reactance resonates the parallel combination of holder capacitance
and circuit capacitance. As such, it's quite affected by the circuit around
the crystal. When the crystal is operated in a parallel resonant mode as
described, the Q of the overall resonant circuit is much lower than the
crystal's resonant Q.

Joe
W3JDR