The main component of garnet

Garnet composition is more complex, different elements constitute different combinations, so the formation of a series of homogenous garnet group. Its general formula is A3B2(SiO4)3, where A represents the bivalent element (calcium, magnesium, iron, manganese, etc.), B is the trivalent element (aluminum, iron, chromium and titanium, vanadium, zirconium, etc.). The common garnet is magnesium aluminum garnet, which contains chromium and iron elements and is red blood, purple red and brown red; The second is the ferroalgarnet, purplish red, inclusion-developed crystals, can be figured out starlight; Magnesium iron garnet is light rose-purple red, is one of the important varieties of garnet gems; Calcium-aluminum-garnet contains trace amounts of vanadium and chromium ions, so it has a green variety called top quality.
Due to the similar radius of the trivalent cation, it is easy to have isomorphic substitution between each other. The divalent cations are different, because Ca has a larger plasma radius than Mg, Fe and Mn, it is difficult to substitute with them. Therefore, garnets are usually divided into two series:
(1) Aluminum: Mg3Al2(SiO4)3-Fe3Al2(SiO4)3-Mn3Al2(SiO4)3
It is a homomorphic series composed of small radius Mg, Fe, Mn and other bivalent cations and Al as the main trivalent cations. The common varieties are magnesium aluminum garnet, iron aluminum garnet, manganese aluminum garnet.
Calcium series: Ca3Al2(SiO4)3-Ca3Fe2(SiO4)3-Ca3Cr2(SiO4)3
It is a large radius of bivalent cationic Ca homomorphic series, common calcium aluminum garnet, calcium iron garnet, calcium chromium garnet. In addition, the lattice of some garnets is also supplemented with OH ions, forming water-containing subspecies, such as hydrocalcium-aluminum-garnet. Due to extensive isotropic substitution, the chemical composition of garnet is usually very complex, and the composition of natural garnet is usually a transition state of isotropic substitution, and few end member components of garnet exist.