Roeblingite
Roeblingite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₆Mn²⁺Pb₂(Si₃O₉)₂(SO₄)₂(OH)₂·4H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 3; specific gravity 3.433; Dull to somewhat resinous luster; optically biaxial.
IMA symbol Roe, grandfathered status — known before the IMA’s founding, named in 1897.
Occurs as nodular masses in calcium silicate lenses containing abundant garnet (Franklin, New Jersey, USA); as fracture fillings in a metamorphosed Fe{Mn orebody (Lº angban, Sweden).
It is found associated with Garnet, titanite, zircon, phlogopite, axinite, willemite, datolite, barite, calcite, arsenopyrite, sphalerite, rhodonite, rhodochrosite.
The name refers to Colonel Washington Augustus Roebling (1837–1926), of Trenton, New Jersey, USA, distinguished American civil engineer, mineral collector.