Retro, the history of a crystal (pressure,temperature, etc)is only relevant insofar as it determines it's structure, whether or not it has piezoelectric properties. Quartz doesn't acquire frequencies, the frequency is determined by its dimensions. This can be demonstrated by changing the dimensions of a crystal thus changing some or all of it's resonant frequency. If the piezolectric resonant frequency of crystals had any relevance to their supposed medicinal properties then crystal therapists would be more interested in this than their colour. Wood has piezoelectric properties too but presumably too low a frequency for such elevated creatures as humans, probably more suited to creatures such as gastropods or oligochaete worms.. :o)