Piezo-electric quartz has the property, when subjected to mechanical pressure, of producing an electric charge, the strength of which varies in relation to the pressure and, conversely, of converting into mechanical pressure the differences in electric potential to which it is subjected.
By reason of this property, piezo-electric quartz is used in the electrical equipment industry for various purposes : the manufacture of microphones, loudspeakers, instruments for transmitting or receiving ultrasonic waves, instruments for fixed frequency oscillations, etc.
The piezo-electric quartz falling in this subheading is generally in the form of thin sheets, plates, rods, etc., obtained by sawing synthetic quartz with a precision-cut along the line of electrical axis.