The one that is extensively used as a piezoelectric material is:

First, let us recall the physical principle involved. The piezoelectric effect is the phenomenon in which certain anisotropic crystalline solids develop an electric potential difference across opposite faces when mechanical stress is applied, and conversely undergo mechanical deformation when an external electric field is placed across them. Thus, a substance suitable for piezoelectric applications must have a crystal structure that lacks a centre of symmetry so that displacement of charge centres under stress can create a net dipole moment.

Now, among the substances listed in the four options we examine their crystal nature one by one.

We have Option A, Tridymite. Tridymite is one of the high-temperature polymorphs of silica, $$\mathrm{SiO_2}$$, that crystallises in an orthorhombic or hexagonal form only at temperatures >870 °C. Although it is crystalline, it is rare, unstable at room temperature, and therefore is not commonly employed in practical devices.

Next we come to Option B, Quartz. Quartz (also $$\mathrm{SiO_2}$$) possesses a trigonal crystal structure at ordinary temperatures that inherently lacks a centre of symmetry. This lack of inversion symmetry fulfils the chief requirement for strong piezoelectric behaviour. Natural and synthetic quartz crystals are cut in specific orientations (AT-cut, BT-cut, etc.) so that when a mechanical pressure is applied, a measurable voltage appears across selected faces and vice versa. Because of its mechanical strength, chemical inertness, ease of growth in large flawless crystals, and stability over a wide temperature range, quartz is extensively used in piezoelectric oscillators, resonators, microphones, pressure sensors, and crystal clocks.

Option C, Amorphous silica (commonly called fused silica or silica glass), by definition lacks a long-range ordered crystal lattice. In the absence of periodic ionic arrangement, no net dipole can be generated by external stress, so amorphous silica is non-piezoelectric.

Lastly, Option D, Mica, although crystalline and electrically insulating, belongs to a different family of layered alumino-silicate minerals. Its crystal class (monoclinic 2/m) possesses a centre of symmetry, which cancels out the piezoelectric effect. Thus mica is widely used as an electrical insulator and dielectric but not as a piezoelectric material.

Among all the candidates, the only substance that satisfies the crystallographic criterion and is also extensively utilised in commercial piezoelectric devices is quartz.

Hence, the correct answer is Option B.