Besides quartz, the opposite substances that show the piezoelectric result are Rochelle salt and tourmaline. Rochelle salt exhibits the greatest piezoelectric result, but its applications are limited to manufacture of microphones, headsets and loudspeakers. It truly is since the Rochelle salt is mechanically the weakest and strongly afflicted by humidity https://consumer-electronics-crys04826.mybjjblog.com/electronics-crystal-oscillators-no-further-a-mystery-47540552