Penfieldite Locality: Margarita Mine, Caracoles, Sierra Gorda District, Tocopilla Province, Antofagasta Region, Chile Picture width 2.5 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Penfieldite
A rare lead hydroxychloride named for Yale mineralogist Samuel Penfield, published in 1892.
Intro adapted from Wikipedia (CC BY-SA).
Penfieldite is an IMA-recognized mineral species in the halide class, with the chemical formula Pb₂Cl₃(OH).
It crystallizes in the hexagonal crystal system (space group P-6).
Key properties: specific gravity 5.82–6.61; Adamantine to greasy luster; optically uniaxial.
IMA symbol Pfd, grandfathered status — known before the IMA’s founding, named in 1892.
An alteration product of lead-bearing slag immersed in seawater (Laurium, Greece; Baratti Beach, Italy); in an oxidized hydrothermal lead deposit (Sierra Gorda district, Chile).
It is found associated with Paralaurionite, phosgenite (Laurium, Greece); fiedlerite, cotunnite (Baratti Beach, Italy).
The mineral was named to honor Professor Samuel Lewis Penfield (1856–1906), American mineralogist and mineral chemist, Yale University, New Haven, Connecticut, USA.