As-grown Mg2Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators.

In the face-centered cubic lattice Si centers occupy the corners and face-centered positions of the unit cell and Mg centers occupy eight tetrahedral sites in the interior of the unit cell.

[2] It can be produced by heating silicon dioxide, SiO2, found in sand, with excess magnesium.

[5] Magnesium silicide is used to create aluminium alloys of the 6000 series, containing up to approximately 1.5% Mg2Si.

Its as-grown crystal exhibit n-type conductivity, but it can be changed to p-type by doping with Ag, Ga, Sn and possibly Li (at high doping level).