Barium carbonate also known as witherite, is a chemical compound used in rat poison

Rat poison

Rodenticides are a category of pest control chemicals intended to kill rodents.Single feed baits are chemicals sufficiently dangerous that the first dose is sufficient to kill....

, brick

Brick

A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...

s, ceramic glazes and cement

Cement

In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

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Witherite crystallizes in the orthorhombic system. The crystal

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

s are invariably twinned together in groups of three, giving rise to pseudo-hexagonal forms somewhat resembling bipyramidal crystals of quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

, the faces are usually rough and striated horizontally.
The mineral is named after William Withering

William Withering

William Withering was an English botanist, geologist, chemist, physician and the discoverer of digitalis.-Introduction:...

, who in 1784 recognized it to be chemically distinct from barytes.