: a mineral (Mn,Mg,Ca,Pb)(AsO4)(OH)5 composed of a basic arsenate of manganese often with other elements (such as magnesium, calcium, lead) and occurring in black prismatic crystals and grains (hardness 4.5, specific gravity 3.5)
Word History
Etymology
German synadelphit, from Greek synadelphos one that has a brother or sister (from syn- + adelphos brother) + German -it -ite