The biggest distinction between mechanical and quartz watches is the use of a battery. Quartz watches are powered by a battery and mechanical watches are powered by gears and springs. You’ll notice that the second hand on a mechanical watch has almost continuous motion while the second hand of a quartz watch ticks once per second. 

 QUARTZ WATCHES

When a watch says “Quartz," it means that the watch is powered by a movement which regulates time through the use of a crystal made out of the mineral quartz. Quartz watches still have gears to turn the hour, minute, and second hands (unless the watch does not have hands, i.e. digital watches), as well as any other complications (explained later), but gears in a quartz watch are turned by an electric stepping motor (a motor that can move a prescribed distance each time it is engaged) that is powered by a battery.The mineral quartz has the property of being piezoelectric. This means that when any type of mechanical stress is introduced to the material's structure, it produces an electrical impulse. The opposite is also true, meaning that the material vibrates when charged with electricity. 

The basic concept behind a quartz watch movement is relatively simple. A tiny circuit and microchip use a battery to charge a tuning-fork-shaped quartz crystal, causing it to vibrate or oscillate. The microchip is calibrated to measure this vibration in order to regulate an electrical signal that pulses exactly once every second (32,768 oscillations/second!). This electrical pulse tells the stepping motor to turn the hands one second worth of motion.

Quartz is an extremely abundant mineral and the workings of a basic quartz movement are fairly easy to mass produce. Consequently, quartz watches can be produced for very low cost while maintaining a high level of accuracy. Interestingly enough, a quality quartz watch will keep time as good or better than the highest-end mechanical watches.

MECHANICAL WATCHES

A mechanical watch is powered by gears and springs. It uses calibrated motion to regulate time. The basic principle behind a mechanical watch is as follows; the user turns the crown of the watch to wind a spring (called the mainspring), and this spring puts force on the first gear in a train of gears. Similar to a transmission, this gear train uses leverage to reduce the force significantly and apply a small amount of pressure to a mechanism called the escapement. This escapement does exactly what the name suggests; it allows the energy stored in the mainspring to escape very slowly, and it regulates the release of this energy in order to turn the hands of the watch at the correct speed to keep time.

If quartz watches perform similarly to mechanical watches, then why can mechanical watches be so much more expensive?

Mechanical watches were the only way to keep time without a clock nearby before quartz watches were invented. Mechanical watch mechanisms were some of the most advanced technology of their time, and mechanical pocket watches were in such high demand in the late 1800's and early 1900's that a massive industry emerged. As a result, many mechanical watches have held their value through pure historical and heritage related factors.

The major functional benefits of mechanical watches are that they never run out of battery and they are not disposable. Quality mechanical watches are made to last forever if taken care of.

There is an overwhelming variety of quality, decoration, and function that distinguishes some watches from other watches in addition to the heritage, tradition, and branding of companies responsible for building those watches. The level of precision, engineering, and detail that goes into fabricating some of the world's most complicated mechanical watches is difficult to comprehend.

The true value of a mechanical watch in the modern world, however, is the craftsmanship and the story. Humankind has been captivated by feats of elegance and precision for hundreds of years, and mechanical watches represent the epitome of beauty in function. The romance involved with quality mechanical watches continues to infect more people each year, even as the role that watches play in our lives evolves into something much more than keeping time.