Roeblingite

This sample of roeblingite is displayed in the Smithsonian Museum of Natural History. Roeblingite contains calcium, manganese and lead with the composition Ca₆MnPb₂(Si₃O₉)₂(SO₄)₂(OH)₂.4H₂O. This sample is about 6x6 cm and is from Franklin, New Jersey. It is described as a silicate, and more particularly as a cyclosilicate.