1. Chemical Composition:
* Elements: Some minerals consist of a single element, like sulfur (S) or diamonds (C).
* Oxides: These minerals contain oxygen bonded to one or more other elements, like hematite (Fe₂O₃) and quartz (SiO₂).
* Sulfides: Minerals composed of sulfur bonded to a metal, like pyrite (FeS₂) and galena (PbS).
* Sulfates: Minerals with sulfur bonded to oxygen and a metal, like gypsum (CaSO₄·2H₂O) and barite (BaSO₄).
* Halides: These minerals contain halogens (like chlorine, fluorine, bromine, and iodine) bonded to a metal, like halite (NaCl) and fluorite (CaF₂).
* Carbonates: Minerals with the carbonate ion (CO₃²⁻) bonded to a metal, like calcite (CaCO₃) and dolomite (CaMg(CO₃)₂).
* Phosphates: Minerals containing the phosphate ion (PO₄³⁻) bonded to a metal, like apatite (Ca₅(PO₄)₃(OH,F,Cl)).
* Silicates: These are the most common group of minerals, containing silicon and oxygen in a variety of arrangements, like feldspar (KAlSi₃O₈) and mica (KAl₂(AlSi₃O₁₀)(OH)₂).
2. Crystal Structure:
* Isometric: Minerals with equal dimensions in all directions, like pyrite and halite.
* Tetragonal: Minerals with two equal dimensions and a different third, like zircon.
* Orthorhombic: Minerals with three unequal dimensions at right angles, like topaz.
* Monoclinic: Minerals with three unequal dimensions with two at right angles and the third at a different angle, like gypsum.
* Triclinic: Minerals with three unequal dimensions and no right angles, like turquoise.
* Hexagonal: Minerals with six-sided symmetry, like quartz and beryl.
* Trigonal: Minerals with three-sided symmetry, like calcite and tourmaline.
Note: The above categories are not mutually exclusive, and many minerals can be classified into multiple groups.
Subgroups within specific groups:
While there's no official "subgroup" system for minerals, within certain mineral groups, you might find further classifications based on specific features:
* Silicates: Subdivided into groups like feldspars, pyroxenes, amphiboles, and micas based on the arrangement of silicon and oxygen tetrahedra.
* Oxides: May be further divided into groups based on the metal involved, like iron oxides (hematite, magnetite) or aluminum oxides (corundum).
It's important to understand that the classification of minerals is a complex and dynamic field. New mineral discoveries and advancements in scientific techniques often lead to modifications and refinement of existing classifications.
