Ca2MgAlAlSi2O7

Ca2MgAlAlSi2O7 is a silicate mineral of the pyroxene group. It is a rare mineral that is typically found in some igneous rocks, particularly in aluminous lamproites. The mineral is named euphrosine, with the systematic name calcium magnesium aluminium alumino silicate (IV).

Euphrosine was first discovered in 1898 in the United States and was named after the Greek word "euphrosyne," meaning joy, with the suffix "-ine" used as a mineral name suffix.

Chemically, euphrosine has the formula Ca2MgAlAlSi2O7 and has a trigonal prismatic crystal structure, with space group P3121. Its mean crystal size ranges from 0.2 to 1 centimeter. The mineral is typically brown or colorless with a transparent to translucent appearance.

Properties of euphrosine include a Mohs hardness of 6, a vitreous luster, and a conchoidal fracture. It also exhibits biaxial positive optical properties, with a refractive index of approximately 1.64 and a dispersion of 0.026. Euphrosine has a density of approximately 3.28 g/cm3 and an average atomic volume of 50.5 Å3.

Euphrosine is known to occur in nepheline syenites, belonging to the spilite group of rocks from the San Carlos region of the Moon of Pluto's moons. It is formed through high-temperature hydrothermal alteration of primary peralkaline igneous rocks.