Types of Crystals

Crystals are defined as solid minerals, in which component ions, atoms and molecules are arranged in a regular structure. It is this orderly arrangement of the constituent particles that give all types of crystals a straight edge and flat surface. Examples of common crystals include salt, sugar, snowflakes, gemstones, rubies and diamonds. Each of the crystal type possesses a specific shape and different properties, based on which they are classified.

Different Types of Crystals

Crystals are used in our day-to-day life for a number of purposes. Whenever we add common salt in cooking foods, we are ingesting salt crystals. On the contrary, precious and semiprecious crystals are worn as jewelry. Another use of crystal is metaphysical healing. Likewise, several types of crystals are identified, which are basically categorized according to their shape and properties.

Crystal Types: Based on Shape
As per the shape or structure, there are seven types of crystal lattice systems:

• Cubic - Precisely known as isometric crystal (e.g., halite), this type comprises crystals that measure the same length in all axes. They may be four sided (cubic), eight sides (octahedrons) and twelve sided (dodecahedrons).
• Monoclinic - Monoclinic crystals (e.g., orthoclase) are characterized by lattice vectors of different lengths. Their structure resemble a rectangular prism having a parallelogram base.
• Triclinic - In triclinic crystals (e.g., microcline), all the three vectors have different lengths, thus exhibiting somewhat strange shapes.
• Trigonal - Simply speaking, trigonal crystals (e.g., dolomite) are cubic crystals, when the latter is stretched along the body diagonal.
• Tetragonal - Tetragonal crystals (e.g., wulfenite) are more or less similar to the cubic type, except that one lattice vector is stretched to a certain length. Structurally, a tetragonal crystal resembles a rectangular prism having a square shaped base.
• Orthorhombic - This type of crystal appears like a tetragonal crystal, when viewed from the side. An orthorhombic crystal (e.g., aragonite) has a rectangular prism and a rectangular base.
• Hexagonal - The structural symmetry of a hexagonal crystal (e.g., beryl) is similar to a right prism. When viewed in cross section, you will get a regular hexagonal shape.

Crystal Types: Based on Properties
Crystals can be divided into four types, according to their physical and chemical properties:

• Ionic Crystals - Crystals in which the constituent atoms are bound together by strong ionic or electrostatic bonds. Example of ionic crystal type is common salt (NaCl); the sodium ion and chloride ion are bonded non-covalent, electrostatic bonds.
• Covalent Crystals - As the name signifies, the component particles of covalent crystals exhibit strong covalent bonding. The most precious stone, diamond is an example of covalent crystal.
• Metallic Crystals - In general, metallic crystals (e.g., nickel and copper) have a very high meting and boiling points. In this type of crystal, the atoms are present in the lattice sites, which enable the outer electrons to move freely.
• Molecular Crystals - Unlike ionic and covalent crystals, the constituents of molecular type are bonded by weak hydrogen or van der Waal's forces. Thus, a molecular crystal (e.g., sugar) usually has a low melting point.

Crystals and Their Meanings

As per scientific studies, certain types of crystals and gemstones have varying amounts of natural vibrational energies and metaphysical healing power. Crystal healing is a phenomenon, wherein the properties of crystals and stones are used to manipulate our thoughts and emotions, so as to help manage anger, stress, depression, disease symptoms and other negative energies in the body. With the increased popularity of crystal healing, rigorous studies have been done on crystals and their meanings. To mention a few healing stones, jade crystal is good for heart health, emerald for respiratory system, amethyst crystal for headache, rose quartz for emotional stress, lapis crystal for anxiousness, ruby for infections and malachite crystal for stomach related problems.

So, this was a brief overview on the classification and usage of crystals. The commercial value of crystals and stones are decided according to the various aspects such as color, shape, size, composition, hardness, optical characteristics, durability, etc. Likewise, you can also find other ways of categorizing crystals.