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A quartz clock is a clock that functions by means of an electronic oscillator regulated by a quartz crystal to keep time. Quartz clock are preferred over mechanical clocks because they are about an order of magnitude more accurate.  This is due to the unique quality of  the quartz crystal oscillator that makes it to create a signal with very precise frequency. Warren Marrison and J.W. Horton of Bell Telephone Laboratories are known to be the first to build a quartz clock.

Photo from wikipedia http://en.wikipedia.org/wiki/Quartz_clock^{Image Removed}

EXPLANATION

Quartz is a crystalline mineral, silicon dioxide, the principal component of sand which could be found in abundance on the earth's surface.  However, manufacturers use synthetic or man-made quartz crystals instead of natural ones because they have more consistent properties.  Many materials can be formed into plates that will resonate but quartz is the most preferred material for time keeping because of two special qualities that it has: its piezoelectric quality and its stability in every time, place and condition. 

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The quartz tuning forks are made so accurate that they vibrate at 32,768 times per second give or take one six-hundredth.  In order to get the forks tuned to this frequency, the designers first add some deposits of gold at the ends of the tines to lower the fork’s vibration frequency.  Then a laser zaps tiny bits of the gold off until the desired frequency is reached.

Photo from wikipedia http://en.wikipedia.org/wiki/Quartz_clock^{Image Removed}

MECHANISM

I. The quartz oscillator receives an electrical charge from an integrated circuit, which gets its power from the watch battery (or, in the case of a battery-less watch, the poser storage cell). The electricity makes the quartz vibrate, or oscillate, at the rate or 32,768 times per second. (Quartz crystals can be cut to vibrate at a huge range of frequencies. the bigger the piece, the slower it vibrates.)

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A cantilever made of quartz(E = 10¹¹ N·m^−2^ = 100 Gpa and ρ = 2634 kg·m^−3 with a length of 3 mm and a thickness of 0.3 mm has thus a fundamental frequency of around 33 kHz. The crystal is tuned to exactly 2¹⁵ = 32,768 Hz or runs at a slightly higher frequency with inhibition compensation .

REFERENCES

1. Wikipedia  http://en.wikipedia.org/wiki/Quartz_clock^{Image Removed}
2. Buchanan, Norma http://www.capetowncorp.com/whatsnew/quartz.html^{Image Removed}
3. Hammack, Bill http://www.engineerguy.com/videos/video-quartz-watch.htm^{Image Removed}