How is positive feedback supplied in a Pierce oscillator?

A Pierce oscillator is a highly stable electronic oscillator circuit commonly found in digital clocks, radios, and microcontrollers. It is functionally a derivative of the Colpitts oscillator, but it replaces the traditional inductor with a quartz crystal. In this design, the quartz crystal operates in its inductive region and provides a high-Q resonant path. Positive feedback, which is required to sustain continuous oscillation, is routed directly through this quartz crystal from the output back to the input. Other options refer to different oscillator topologies. For instance, a tapped coil is a hallmark of a Hartley oscillator, while link coupling is generally used for impedance matching between amplifier stages, not for supplying feedback in a Pierce oscillator.