Barium carbonate is a white solid. It does not dissolve in water. It reacts with acids to make barium salts. It turns into barium oxide and carbon dioxide when heated. It reacts with sulfuric acid to make barium sulfate though.
Barium carbonate occurs as witherite. Witherite is the main source of barium salts. It is more easily turned into other barium compounds than barium sulfate, barite. It is heavily mined in Northumberland. It turns into barium sulfate when water containing sulfates flows through it.
Barium carbonate can dissolve in stomach acid, so it is toxic. There is a controversy over whether it should be used as a glaze.