Small crystals of seamanite from the Chicagon Mine in Iron County, Michigan . Held in the A. E. Seaman Mineral Museum . — Photo: Chris857 · CC BY-SA 3.0
Seamanite
A rare yellow-to-pink manganese boron phosphate forming small needles, named for Arthur Seaman.
Intro adapted from Wikipedia (CC BY-SA).
Seamanite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Mn²⁺₃B(OH)₄(PO₄)(OH)₂.
It crystallizes in the orthorhombic crystal system (space group Pbnm).
Key properties: Mohs hardness 4; specific gravity 3.08–3.13; refractive index 1.656; optically biaxial.
IMA symbol Sem, grandfathered status — known before the IMA’s founding, named in 1930.
Found in fractures cutting siliceous rock.
It is found associated with Sussexite, calcite, manganese oxide.
The mineral was named to honor Professor Arthur Edmund Seaman (1858–1937), American mineralogist, Michigan College of Mining and Technology, Houghton, Michigan, USA, who first noted the mineral.