Calcium oxalate (in archaic terminology, oxalate of lime) is a chemical compound that forms envelope-shaped crystals, known in plants as raphides. A major constituent of human kidney stones, the chemical is also found in beerstone, a scale that forms on containers used in breweries. Its chemical formula is CaC2O4 or Ca (COO)2.
Many plants accumulate calcium oxalate as it has been reported in over 1000 different genera of plants. The calcium oxalate accumulation is linked to the detoxification of calcium (Ca) in the plant.