A crystal is a solidified form of a substance in which the
atoms or
molecules are arranged in a definite pattern that is repeated regularly in
three dimensions. Crystals form when
saturated or
supersaturated solutions deposit layer upon layer or a
substrate, initially onto a surface and then upon each other. This process generally forms a solid with remarkable
geometric properties. Because of the mechanics of crystal formation, the slower the crystal forms, the larger and more perfect it will ultimately be.
The beauty and perfection of crystals has long made them prized possessions for human beings.
Diamonds are generally thought to be the most valuable and beautiful crystals. They are composed of a lattice of pure
carbon, as is
graphite,
buckminsterfullerum, and
carbon nanotubes. The regular structure, and the properties of
carbon, make all of these forms exceptionally strong.
Other fascinating properties of crystals are exploited in
electronics:
quartz crystals oscillate with sufficient regularity to be used as timepieces, semi-conducting crystals form the basis for modern
electronics. The
quantum properties of the crystal structure allow fascinating electric properties: one can actually make a
transistor from a
carbon nanotube twisted properly. Our increasing understanding of
quantum mechanics and crystals has allowed the development of the
laser and numerous other inventions.
The method in which crystal structure is determined is a process called
x-ray crystallography. It was through these means that the structure of
DNA (
deoxyribonucleic acid) was determined by
Watson and
Crick.
According to the principle of
evolutionary pressure and
selfish gene theory, some people have offered the supposition that the development of life on earth, and perhaps elsewhere in the universe, began with crystals.