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Minerals are natural compounds formed through geological processes. The term "mineral" encompasses not only the material's chemical composition but also the mineral structures. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms (organic compounds are usually excluded). The study of minerals is called mineralogy.
1 What is a mineral ?
To be classified as a "true" mineral, a substance must be a solid and have a crystal structure. It must also be a naturally-occurring, homogenous substance with a defined chemical composition. The chemical composition may vary between end members of a mineral system. For example the plagioclase feldspars comprise a continuous series from sodium-rich albite (NaAlSi3O8) to calcium-rich anorthite (CaAl2Si2O8) with four recognized intermediate compositions between. Mineral-like substances that don't strictly meet the definition are sometimes classified as mineraloidA mineraloid is a mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorphous glass and not a crystals.
A crystal structureIn mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a unit cell a set of atoms arranged in a particular way, which is periodically repeated in three dimensions on a latti refers to the orderly geometric spatial arrangement of atomFor alternative meanings see atom (disambiguation). An atom is a microscopic structure found in all ordinary matter around us. Atoms are composed of 3 types of subatomic particles: electrons, which have a negative charge; protons, which have a positive chs in the internal structure of a mineral. There are 14 basic latticeIn colloquial usage, a lattice is a structure of crossed laths with open spaces left between them. The term is used in various technical senses, all of which have some geometrical relation to the dictionary definition. In one mathematical usage, a lattice arrangements of atoms in three dimensions in the six crystal systems, and all crystal structures currently recognized fit in one of these 14 arrangements. This crystal structure is based on regular internal atomic or ionic arrangement that is often visible as the mineral form. Even when the mineral grains are too small to see or are irregularly shaped the crystal structure can be determined by x-rayIn the NATO phonetic alphabet, X-ray represents the letter X. Rontgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz to 60 EHz). X-ray analysis and/or optical microscopyMicroscopy is any technique for producing visible images of structures or details too small to otherwise be seen by the human eye. With the exception of techniques such as force microscopy and electron tunnel microscopy, microscopy usually involves the di.
Chemistry and crystal structure define together a mineral. In fact, two or more minerals may have the same chemical composition, but differ in crystal structure (these are known as polymorphs). For example, pyrite and marcasite are both iron sulfide. Similarly, some minerals have different chemical compositions, but the same crystal structure: for example, halite (made from sodium and chlorine), galena (made from lead and sulfur) and periclase (made from magnesium and oxygen) all share the same cubic crystal structure.
Crystal structure greatly influences a mineral's physical properties. For example, though diamond and graphite have the same composition (both are pure carbon), graphite is very soft, while diamond is the hardest of all minerals.
There are currently just over 4,000 known minerals, according to the International Mineralogical Association, which is responsible for the approval of and naming of new mineral species found in nature.
