granaatit

Granaatit is the Finnish name for garnet, a group of closely related silicate minerals with a common crystal structure and general formula X3Y2(SiO4)3. The X site typically hosts divalent cations such as calcium, magnesium, iron(II), or manganese; the Y site is usually aluminum, iron(III), or chromium. Garnets occur in a wide range of chemical compositions, corresponding to varieties such as almandine (Fe2+, Al), pyrope (Mg, Al), spessartine (Mn, Al), grossular (Ca, Al), andradite (Ca, Fe), and uvarovite (Ca, Cr). They crystallize in the cubic (isometric) system and commonly form well-shaped dodecahedra or trapezohedra. Colors vary from red, orange, and yellow to green and colorless, depending on composition.

Garnet minerals form in metamorphic rocks such as schists and granulites, and in some igneous rocks, including granites and diorites, under high-temperature and pressure conditions. They are often used as index minerals to indicate metamorphic grade. Industrially, garnet is used as an abrasive and gemstone; garnet crystals are also employed in waterjet cutting and filtration media.

The name garnet derives from Latin granatus, meaning grain or seed, referencing the mineral’s granular appearance in rocks.