Crystallography is the scientific study of crystals.
Crystallography is the branch of earth science dedicated to the study of crystals. A crystal is a naturally occurring form that is created when a liquid or gas changes into a solid. Crystals are categorized by their different geometric shapes defined by angles and three axes: the vertical C axis, the horizontal B axis and the third dimensional A axis, which intersects at the same point as the C and B axes.
Isometric
Isometric crystals are the simplest form of crystals. Similar in shape to a square box, they are sometimes referred to as cubic crystals. All axes are equal in length and all angles are 90 degrees. The equal angles and axes create a completely symmetrical form. Diamonds are a familiar type of isometric crystal.
Tetragonal
If an isometric crystal could be stretched or flattened into a rectangular shape, the result would be a tetragonal crystal. Tetragonal crystals have 90 degree angles and equal A and B axes. The length of the C axis is either shorter or longer than the other two. Zircon is classified as a tetragonal crystal.
Hexagonal
Hexagonal crystals have a unique composition based on four axes instead of three. The C axis is vertical as in the other systems. The three remaining axes--A1, A2 and A3--are all on the same plane, equal in length and intersect with the C axis at 90 degrees. The three A axes intersect at the same point to create six equal angles of 60 degrees each. Aquamarine is an example of a hexagonal crystal.
Orthorhombic
The axes of orthorhombic crystals are each a different length and intersect at 90 degree angles. They are similar in shape to tetragonal crystals, but are differentiated by the unequal lengths of all three axes. Topaz is an orthorhombic crystal.
Monoclinic
Monoclinic crystals have three unequal length axes. The A and C axes intersect at an oblique angle, and the B axis passes through at 90 degrees. Monoclinic crystals are similar in shape to tetragonal crystals but do not have equal angles. The majority of crystals fall into the monoclinic system. Gypsum is a common example of a monoclinic crystal.
Triclinic
The axes and angles of triclinic crystals are each of different measurements with none of the angles forming at 90 degrees. Triclinic crystals are almost completely asymmetrical. Turquoise forms as a triclinic crystal.
Trigonal
Students of crystallography in the United States learn the six basic crystal systems. In some other areas of the world, most notably Britain, a seventh system is introduced. The trigonal system is closely related to the hexagonal system. The difference between a hexagonal crystal and a trigonal crystal is that the edges of a trigonal crystal are rounded instead of sharp. Sapphire is a trigonal crystal.
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