What are crystals?

Crystals are solid substances that are naturally formed into regular geometric, angular shapes. Atoms in a crystal are arranged in a repeating, orderly pattern. Crystals can be found in computers and television sets, in jewelry, in the food we eat, and even in our own bodies. Some crystals such are gems like diamonds and rubies, are large enough to be seen by the naked eye.Crystals of normal table salt can be seen under a magnifying glass. Most crystals, however, are so small that they can only be observed under a high-powered microscope.

All crystals can be classified into seven systems. Sometimes a crystal is formed when water evaporates, and substances dissolved in the water gradually grow into crystal. Other crystals are formed under great pressure.

A crystal can be made up of atoms of just one type -- with each atom having the same size and shape. For example, a diamond crystal is made up entirely of carbon atoms.

Some crystals are made up of certain kinds of atoms, called ions. Ions are atoms or group of atoms that carries either positive or negative electrical charge. To form an ionic crystal, at least two opposite charge, that is one negative and one positive, are needed. The attractive forces between the two opposite charges hold the crystal together.

Crystal can also be made up of groups of atoms that are bonded together to form molecules. Each molecule acts as a building block in the crystal. For example, one kind of sugar (known chemically as glucose) is made up of glucose molecules. Each molecule contains atoms of carbon, hydrogen, and oxygen.