Types of Crystal Structure and How Crystals are formed? Crystal and Mineral Identification

What are types of Crystal Structure and how crystals are formed?

What are types of Crystal Structure and how crystals are formed? What is crystal structure definition? This is actually the question, the answer of which will help you in the identification of Gemstones and minerals. A crystal structure, basically, is a specific form of a gemstone or a mineral, in which there presence a specific arrangements of ions, molecules, atoms inside. It is this very specific shape and arrangements of atoms , ions and molecules which gives the minerals and Gemstones, a particular shape or Structure physically. 

Following crystal structures of gemstones and minerals have been defined by the scientists and the researchers. 

1. Crystals by Shape or grouped by Lattices
2. Recognition of crystals by properties

Let us first discuss crystals grouped by Lattices.

1-Shape of Crystals or Crystals Grouped by Lattices

In Lattices group of crystals, the researchers have defined 7 different crystalline shapes or structures for identification of crystals which are here below:-

1. Tetragonal: This type is similar to cubic structure however they are longer on axis than the other. The tetragonal system has 3 axes which all meet at 90 degrees. Though being square base in its crystal structure, it's height will be longer than the axis. These Crystals form double pyramids and prisms.
   
2. Cubic or Isometric: They have sometime octahedrons having 8 faces and some times dodecahedrons having 10 faces. Examples are flourite, pyrite.
    
3. Orthorhombic: They are like Tetragonal with one difference, they are not square in cross section. Such crystals form rhombic prisms and dipyramid. Aragonite , topaz is example. 
   
4. Hexagonal: When These crystals will have 6 sided prism and hexagon. Beryl is an example. Other examples are Emeralds. 
    
5. Trigonal: These have single 3 gold axis of rotation instead 6 fold like hexagonal division.abhurite, alpha-quartz is an example.   
6. Triclinic: These crystals do not come in a symmetrical form which leads t strangers shaed. Axinite, kynite is an example.  
7. Monoclinic: Like These crystals usually work prisms and double pyramids. Examples are gypsum, orthoclase, muscovite, clinoamphibole, clinopyroxene, jadeite, azurite, and spodumene .  

Crystals Grouped by Properties

There are 4 different crystal categories according to their chemical and physical propertes.

1. Covalent Crystals: A covalent crystal will have strong covalent bond between all atoms. Covalent crystal can be called as a big molecule. Such Crystals are melt on very ugh melting points. Examples are diamond, zircon. 

1. Metallic Crystals: This is very interesting. In the crystal structure,  metal atoms of crystals lays on lattice sites.outer electrons flour outside the latice. Metallic crystals are dense and also having high melting points.  Like Bismuth  
2. Ionic Crystals: The atoms of ionic crystals are bound together by ionic bonds. Such crystals are very hard. They also have a high melting points. 
3. Molecular Crystals: These crystals are held together by non covalent interactions like hydrogen bonding. recognizable molecules within their structures. Such crystals are usually soft and having low melting point. Table sugar is an example. 

These data is based on researches made by researchers. There is no definite rule to define crystals. As new Gemstones and minerals appear in different regions with more complex crystal structure. Than new rules are to be decided. However already researched can help us in recognizing gems and minerals.