What is a Crystal?
There are many scientific explanations of what constitutes a crystal. In simple terms, crystals are formed in the earth’s center. They are minerals; through natural geographical processes solidify into what we call a crystal. What makes a crystal a crystal is its unique chemical composition that is unique to a crystal. Crystals also have specific highly organized atomic lattice matrixes that make them distinct as crystals. They also have specific physical properties that make them crystals as well. A mineral which crystals are composed of can also range in composition from what are termed pure, simple elements as simple salts to complex silicates.
In order for a mineral to be classified as a true mineral as a crystal, it has to have what is called a crystalline structure and be solid in form. A true crystalline structure also has a naturally occurring substance with a specifically-defined chemical structure. A true crystal has an orderly geometrical spatial arrangement of atoms in the internal structure of the crystal.
There are 14 basic lattice arrangements for crystal atoms in the third dimension called “Bravis Lattices”. Each one of these 14 lattices can be further classified into one of seven (7) crystal systems. All the re-organized crystals we see today fit into one of these seven systems.
The structure of a crystal is actually based on the internal, regular atomic and ionic arrangements that are specifically characteristic to a particular form a crystal may take. This is true for even those grains of crystal matter that are too small to see. Those minute crystal grains carry the innate atomic and ionic structures that make them a crystal.
When looking at what is or is not a crystal proper, one then takes into consideration what is called a polymorph. When two minerals have the same chemical structure, but their crystal structure differs, they are called polymorphs. An example of this would be Pyrite and Marcasite which are both iron sulfides, but the atomic structures are not the same. You can also find that minerals may indeed have the same crystal atomic structure, but are not the same chemical composition. Examples with the same crystal structure, but not the same chemical composition, would be halite and galena. Both have the same crystal structure, but halite is composed of sodium and chlorine and galena is lead and sulfur.
So, the next time you see a crystal in the store, you will know they are more than just rocks; they are substances that come from the center of the earth with specific atomic, ionic and chemical compositions that are unique only to crystals.