The pattern in which the atoms and molecules forming a mineral are arranged This controls the shape of the crystal and the properties of the mineral, such as how it splits, the hardness and how light passes through it
for crystalline materials, the manner in which atoms or ions are arrayed in space It is defined in terms of the unit cell geometry and the atom positions within the cell
A scheme by which crystal structures are classified according to unit cell geometry This geometry is specified in terms of the relationships between edge lengths and interaxial angles There are seven different crystal systems
The order in which atoms are arranged in a material These arrangements have a direct effect on the physical properties of the material These arrangements commonly take the form of cubes, rectangular solids, hexagonal solids etc A thorough treatment of crystal structure and other materials issues can be found at the Visualizations in Materials Science WWW site