Among the more than 15 species of garnet recognized by the world's main mineralogists, calderite is one of the rarest. It usually appears in massive nodules of up to 5 cm, which sometimes show a crystallized facet. Its rarity, and the fact that sometimes one can find a larger specimen, make this garnet a very coveted piece for collectors. It was first discovered in a manganese mine in Bangladesh, but later also appeared in Namibia, where better specimens were obtained. These are the only two deposits known.