Axinite-(Mg) is a borosilicate mineral of aluminum, calcium and magnesium of the axinite group, with magnesium as the dominant cation in the place of the structure that can also be occupied by iron and manganese. It was discovered in gem material from Merelani Hills, Lelatema Mts, Manyara Region, Tanzania, which is consequently its type locality. It was initially called magnesioaxinite, referring to its membership in the axinite group and the role of magnesium as the dominant cation. The

International Mineralogical Association Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...

(IMA) later changed its name to axinite-(Mg). Occasionally it has been carved as a collection gem.

Physical and chemical properties

Like the rest of the minerals in the axinite group, axinite-(Mg) belongs to the

triclinic system 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal i ...

, appearing in the form of crystals with the characteristic ax-shaped morphology. Its structure can be described as a sequence of alternating layers of cations coordinated tetrahedrally and octahedrally.

Deposits

The axinite group minerals are found in medium-to-low contact metamorphism, regional or metasomatic environments, in boron-containing environments. Axinite-(Mg) appears more frequently in areas of contact metamorphism. It is a relatively rare mineral, known in about a dozen locations in the world. In addition to the type locality, already indicated, in which specimens with transparent crystals of various colors, up to 3 cm in size, have been found in the area of Lunning, Mineral Co., Nevada (USA), as violet brown crystals. In Spain, axinite-(Mg) associated with crystalline calcite has been found in the diabase of a quarry located in El Zurcido, Adamuz (Córdoba) .

References

Magnesium minerals Silicate minerals Gemstones Triclinic minerals {{silicate-mineral-stub