mineralogy

Mineralogy is the science that studies minerals, the naturally occurring inorganic solids with defined chemical compositions and ordered atomic structures. It investigates how minerals form, their properties, how they occur in the Earth's crust, and how they transform under different environmental conditions. Mineralogy overlaps with crystallography, petrology, and geochemistry, and provides essential information for geology, materials science, and economic geology.

Minerals are classified by chemical composition and crystal structure. Silicate minerals, built on silica tetrahedra, constitute the largest group and include feldspars, quartz, micas, and the pyroxenes and amphiboles. Non-silicate minerals cover oxides, sulfides, carbonates, sulfates, halides, and phosphates. Minerals are also grouped into families based on their crystal systems and structural motifs, such as isometric, monoclinic, or hexagonal.

Physical and optical properties are central to mineral identification. Key properties include crystal habit, cleavage and fracture, hardness (Mohs scale), color, streak, and luster. Optical properties observed under polarized light, such as refractive index and birefringence, aid characterization. Modern mineralogy relies on analytical techniques such as X-ray diffraction, electron microprobe analysis, Raman and infrared spectroscopy, and electron microscopy to determine composition and structure at micro to nanoscale levels.

Formation and occurrence span igneous, sedimentary, and metamorphic environments. Minerals crystallize from melts, precipitate from hydrothermal fluids, or form through solid-state transformation and metasomatic processes. They are central to understanding planetary formation, rock assemblages, and the distribution of economically important resources, including ore minerals and industrial materials.

Historically, mineralogy developed from practical mineral identification to systematic classification and precise structural analysis, with milestones in crystallography and mineral spectroscopy shaping the modern science.