Barite (BaSO4) is a mineral consisting of barium sulfate. It is generally white or colorless, and is the main source of barium. Baryte is the British spelling, and the mineral is also called heavy spar. The radiating form, sometimes referred to as Bologna Stone, attained some notoriety among alchemists for the phosphorescent specimens found in the 1600s near Bologna, Italy by one Mr. Vincenzo Cascariolo. Its Mohs hardness is 3, the refractive index is 1.63 and it has a specific gravity of 4.3-5. Its crystal structure is orthorhombic.

Barite commonly occurs in lead-zinc veins in limestones, in hot spring deposits, and with hematite ore. It is often associated with the minerals anglesite and celestine.

The name barite is derived from the Greek word ????? (heavy). In commerce, the mineral is sometimes referred to as "barytes." The term "primary barite" refers to the first marketable product, which includes crude barite (run of mine) and the products of simple beneficiation methods, such as washing, jigging, heavy media separation, tabling, flotation, and magnetic separation. Most crude barite requires some upgrading to minimum purity or density. Barite that is used as an aggregate in a "heavy" cement is crushed and screened to a uniform size. Most barite is ground to a small, uniform size before it is used as a filler or extender, an addition to industrial products, or a weighting agent in petroleum well drilling mud.

Barite is used in the manufacture of paints and paper. Although barite contains a "heavy" metal (barium), it is not considered to be a toxic chemical by most governments because of its extreme insolubility.