chemical element :
noun A constituent of matter defined by an atom with a specific number of protons, known as the atomic number.
Chemical elements can have isotopes, which means they possess the same number of protons but a different number of neutrons. (based on Foucault et Raoult, 2010).
The periodic table of elements, initiated by Russian chemist Dmitri Mendeleev, represents all elements arranged in increasing atomic number, from left to right and top to bottom.
Classification of Minerals
Based on chemical criteria (types of atoms) and crystallographic criteria (how atoms are arranged), minerals can be grouped into different classes:
- Native elements: Simple substances made up of only one chemical element.
- Sulfides and sulfosalts: Compounds combined with the sulfide ion (S²⁻).
- Oxides and hydroxides: Compounds combined with oxygen (O²⁻) or hydroxide (OH⁻) ions.
- Halides (chlorides, fluorides, etc.): Compounds combined with halogen ions (F⁻, Cl⁻, Br⁻, I⁻, At⁻, etc.).
- Carbonates: Compounds combined with the carbonate ion ([CO₃]²⁻).
- Phosphates: Compounds combined with the phosphate ion ([PO₄]³⁻).
- Sulfates: Compounds combined with the sulfate ion ([SO₄]²⁻).
- Silicates: Compounds formed from silica and oxygen ([SiO₄]⁴⁻, SiO₂, etc.).
Just like in biology, major mineral classes can be subdivided into subclasses or even groups.
This is especially true for silicates, which are divided into seven subclasses depending on the structure of their silicon and oxygen atoms.
Nesosilicates: Composed of isolated tetrahedra, each made of one silicon atom bonded to four oxygen atoms.
Sorosilicates: Made of paired tetrahedra linked by a shared oxygen atom.
Cyclosilicates: Composed of rings of six tetrahedra connected by shared oxygen atoms.
Inosilicates: Made of single chains of tetrahedra linked through shared oxygen atoms.
Double-chain inosilicates: Feature two chains of tetrahedra connected by shared oxygen atoms between chains.
Phyllosilicates: Consist of sheets of tetrahedra where each tetrahedron shares three of its oxygen atoms in two dimensions.
Tectosilicates (e.g., quartz): Built from three-dimensional frameworks where each tetrahedron shares all four of its oxygen atoms with adjacent tetrahedra.