axinite-(Mg)

{{Infobox mineral|boxwidth=|boxbgcolor=|name=Axinite-(Mg)|image=Axinite-(Mg)-396672.jpg|imagesize=260px|caption=Crystal fragment of gem axinite-(Mg) from Merelani Hills, Manyara, Tanzania|category=Silicate mineral|formula=Ca2MgAl2BSi4O15OH|strunz=|system=Triclinic|class=|symmetry=|unit cell=|molweight=|color=Light blue, pink|habit=Crystals with the characteristic axe shape|twinning=|cleavage=Good {100}|fracture=Uneven to subconchoidal|tenacity=Somewhat brittle|mohs= - 7|luster=Vitreous|polish=|opticalprop=|refractive=|birefringence=|pleochroism=|dispersion=|fluorescence=|absorption=|streak=White|gravity=4.97|density=|melt=|fusibility=|diagnostic=|solubility=|diaphaneity=Transparent or translucent|other=|references=}}

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