Formation of Crystals

Solute Stage

• Crystal formation begins with a solution made up of a dissolved form of the substance that will form the crystal (a solute) and a liquid (solvent) that holds the dissolved substance

Saturation

• When a solution holds the maximum amount of solute possible, it is saturated. If conditions change, the solution will no longer be able to hold all of the dissolved matter and it will need someplace to go

Changing Conditions

• If some of the solvent evaporates, there will no longer be enough of it to hold the dissolved matter . Similarly, if the temperature of the solution drops, the solvent will not be able to hold all of the dissolved matter

A Breeding Ground

• To get started, crystals need something to cling to. This can be something as small as a dust particle or something larger, such as an existing crystal (a seed crystal) or any rough surface.

Shapes

• The chemical composition of the solute determines the shape in which the crystal will form. U.S. schools generally teach six crystal shape systems: cubic, tetragonal, hexagonal, orthorhombic monoclinic and triclinic. In other countries, the trigonal shape--which resembles the hexagonal system but has more rounded surfaces--is recognized as a separate system.

Quality

• The quality of the crystal is determined by a variety of factors, including temperature, impurities, pressure and available space.