Shortite in Kimberlite from the Upper Canada Gold Mine, Ontario

Shortite, Na₂Ca₂(CO₃)₃, occurs in the groundmass of micaceous kimberlite dikes from the Upper Canada Gold Mine, Ontario. X-ray, optical, and chemical properties of shortite from the Upper Canada Mine are virtually identical to those of shortite from the Green River Formation, Wyoming. The grains poikilitically enclose phlogopite, magnetite, apatite, and perovskite and are closely associated with calcite, olivine, and aggregates of serpentine in the groundmass of the kimberlite. The groundmass assemblage is interpreted to have precipitated from kimberlite magma at low temperature.