magnesite

noun

1. a mineral, magnesium carbonate, MgCO3, having a characteristic conchoidal fracture and usually occurring in white masses.

noun

1. a white, colourless, or lightly tinted mineral consisting of naturally occurring magnesium carbonate in hexagonal crystalline form: a source of magnesium and also used in the manufacture of refractory bricks. Formula: MgCO 3