Description
The mineral witherite is a barium carbonate with the chemical formula BaCO3. It is named after William Withering (1741–1799), a British physicist and mineralogist. Colorless or milky to brownish-white witherite has a vitreous luster, a white streak color, and a distinct cleavage along the crystal plane [010]. The crystal system is orthorhombic. The average density is 4.3 and the hardness is 3 to 3.5. Witherite is not radioactive. It occurs primarily in low-temperature hydrothermal veins. The type locality is Alston Moor, Cumberland, England. The 18th-century naturalist Dr. Leigh recorded lethal effects after the death of a farmer's wife and child. James Watt Jr. had experimented with the mineral on animals and observed the same lethal properties. Until the 18th century, farmers near Anglezarke used the mineral as a rat poison
