The Isometric or Cubic System

These crystals have three axes that have the same length at right angles to each other. These form into an almost perfect cube. The three axes of the isometric crystals are of equal length and join at right angles to one another. The system is in addition at times referred to as the cubic system. Even though crystals falling under this system display a vast assortment of shapes, they by and large have square or triangular faces.

All crystals of the isometric system have four three fold axes of symmetry, each of which proceeds transversely from corner to corner through the middle of the cubic unit cell. Crystals of the isometric system might also show up to three separate four-fold axes of rotating symmetry. If these axes are there they start from the midpoint of each face through the origin to the middle of the opposite face and correspond to the crystallographic axes. In addition, crystals of the isometric system might have six two fold axes of symmetry that expand from the middle of each edge of the crystal through the origin to the middle of the opposite edge. Minerals of this system could show up to nine diverse mirror planes.

Tetragonal System
Just like the isometric system, Tetragonal crystals have three axes at right angles. However, The Tetragonal Crystal System differs from the Isometric System in the fact that one of its three axes of its axial system stands out, and can be read as the most important axis. This means that crystals (grown in a homogeneous environment) are either flattened or elongated.

Hexagonal System
In crystallography the hexagonal crystal system is one of the seven pattern point groups. It has an equal symmetry as a right prism with a hexagonal base. There is only one hexagonal Bravais lattice, which has six atoms per unit cell.

Graphite is an illustration of a crystal that crystallizes in the hexagonal crystal system. Hexagonal arrangements have also been observed in systems of amphiphiles and constitute one of the types of lipid polymorphism.

Orthorhombic System
These types of crystals have three axes all at right angles however each of them is different in length.

Monoclinic System
The monoclinic system has three axes that have unequal lengths. Two of these interact at right angles while the third axis has an oblique angle to the rest of them.

Triclinic System
Triclinic crystals consist of three axes that are not equal in length and that all intersect at oblique angles.

Along with the systems that crystals are identified with, these also form into different, well-defined shapes that are known as habits. Some of the most well known are tabular, cubic and column. However it is not as sure a categorizing characteristic as it might appear.

Habits can change due to temperature, pressure, composition of the solutions from which the minerals crystallize, differences in composition of minerals and impurities in the mineral etc. for example, fluorite crystals, that are a member of the isometric system, might be in the cubic habit if they were formed in lower temperatures but often times they show up in the octahedral form if they were formed in higher temperatures.

Crystals that are looked at with the bare eye, or those that are looked at under a magnifying glass, in most cases usually identify a mineral, however a mineral will often times challenge classification this way mainly because of the changes that it has had because of erosion or fracturing, how small the crystal is, or the chemical action that the metallic crystal had etc.

For a good number of years now, prospectors and geologists have come up with a basic system of testing in order to identify the physical properties of minerals in the field in order for these to be identified with only elementary scientific equipment and this is done through a process of elimination. The properties and the tests that are done for them, which are simple, have been included as well.