Chapmanite
A rare iron phyllosilicate discovered in 1924, named for University of Toronto geology professor Edward John Chapman.
Intro adapted from Wikipedia (CC BY-SA).
Chapmanite is an IMA-recognized mineral species in the silicate class, with the chemical formula Fe³⁺₂Sb³⁺(Si₂O₅)O₃(OH).
It crystallizes in the monoclinic crystal system (space group Cm).
Key properties: Mohs hardness 2.5; specific gravity 3.69–3.75; Greenish yellow to deep yellow streak; Nonmetallic luster; refractive index 1.92.
IMA symbol Cpm, IMA status: approved, named in 1924.
Found in veinlets cutting gneisses containing varying amounts of graphite (Smilkov, Czech Republic).
It is found associated with Silver (Keeley mine, Canada).
The mineral was named to honor Edward John Chapman (1821–1904), Professor of Geology, University of Toronto, Toronto, Canada.