Crystal System

Atomic arrangement of the atoms of an elementSubstance composed of atoms, each of which has the same atomic number (Z) and chemical properties. The chemical properties of an element are determined by the arrangement of the electrons in the various shells (specified by their quantum number) that surround the nucleus. In a neutral atom, the number of when it is in its solid state. In mineralogy, these are  best classified in terms of their symmetryProperty of an object if some spatial manipulation of it results in an indistinguishable object. A symmetric object can be superimposed on itself by some operation. and correspond to the seven fundamental shapes for unit cells consistent with the 14 Bravais lattices. Six systems are recognized: isometric (cubic), hexagonal, tetragonal, orthorhombic, monoclinic, and triclinic.

1. The isometric systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with (also known as the cubic system) has mutually perpendicular crystallographic axes of equal length. All crystals have four 3-fold axes of symmetry diagonally from corner to corner through the center of the unit cellSmallest repeating unit of a crystalline solid that can be used to describe the entire structure. Unit cells are like templates which can be copied to produce an entire crystal.. They may also have up to three separate 4-fold axes of rotational symmetry from the center of each face through the origin to the center of the opposite face; these correspond to the crystallographic axes.
2. The hexagonal system has three crystallographic axes which intersect at 120 ° and a fourth which is perpendicular to the other three. This fourth axis is usually depicted vertically. The hexagonal system may be subdivided into hexagonal or trigonal divisions based upon whether the vertical axis has 6-fold or 3-fold rotational symmetry.
3. The tetragonal crystal system has three mutually perpendicular axes. The two horizontal axes are of equal length, while the vertical axis is of different length and may be either shorter or longer than the other two. Crystals all have a single 4-fold symmetry axisElement of rotational symmetry. Imaginary axis is placed through a perfect crystal so that during a single rotation about this axis the outline of the crystal form appears identically more than once; 2, 3, 4 or 6 times..
4. The orthorhombic system has three mutually perpendicular axes, each of which is of a different length than the others.  Crystals of this system possess three 2-fold rotation axes and/or three mirror planes.
5. The monoclinic system has three unequal axes. Two axes are inclined toward each other at an oblique angle; these are usually depicted vertically. The third axis is perpendicular to the other two. The two vertical axes do not intersect one another at right angles, although both are perpendicular to the horizontal axis. Monoclinic crystals demonstrate a single 2-fold rotation axis and/or a single mirror plane.
6. The triclinic system has three unequal axes, all of which intersect at oblique angles. None of the axes are perpendicular to any other axis. Crystals possess no symmetry at all.