Witherite Composition,
Crystallization & Structure

Composition. Barium carbonate, BaCO3 = Carbon dioxide 22.3, barium oxide 77.7.

Crystallization. Orthorhombic. Crystals always twinned, forming pseudohexagonal pyramids by the intergrowth of three individuals terminated by brachydomes (Fig. 280). Crystals sometimes doubly terminated; often deeply striated horizontally and by a series of reentrant angles have the appearance of one pyramid capping another.

Structure. In twin crystals, also botryoidal to globular; columnar or granular.

Physical Properties. H. = 3.5. G. = 4.3. Vitreous luster. Colorless, whit, gray. translucent.

Tests. Easily fusible at 2.5 – 3, giving a yellowish green flame (barium). After intense ignition gives an alkaline reaction on moistened test paper. Soluble in hydrochloric acid with effervescence. All solutions, even the very dilute, give precipitate of barium sulphate with sulfuric acid (difference from calcium and strontium). Heavy.

Occurrence. A comparatively rate mineral, most frequently found in veins associated with galena. Found in fine crystals near Hexham in Northumberland and Alston Moor in Cumberland. Occurs at Leogang in Salzburg; near Lexington, Kentucky; Thunder Bay, Lake Superior, Ontario.

USE. A minor source of barium compounds.