Barstowite Locality: Passa Limani Cove slag locality, Passa Limani area, Lavrion District slag localities, Lavrion (Laurion; Laurium) District, Attikí (Attica; Attika) Prefecture, Greece Picture width 4 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Barstowite
A transparent-to-white lead chloride-carbonate with an adamantine luster, from Bounds Cliff in Cornwall.
Intro adapted from Wikipedia (CC BY-SA).
Barstowite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Pb₄(CO₃)Cl₆·H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/m).
Key properties: Mohs hardness 3; specific gravity 5.71; White streak; Adamantine luster.
IMA symbol Bsw, IMA status: approved, named in 1989.
A rare reaction product of sea water with a metal-bearing vein exposed at sea level (Bounds Cliff, England); produced by the action of sea water on lead-bearing slag (Laurium, Greece; Baratti Beach, Italy).
It is found associated with Phosgenite, galena, jamesonite, cerussite, pyrite, sphalerite, chalcopyrite, dolomite, quartz (Bounds Cliff, England).
The mineral was named to honor Richard William Barstow (1947–1982), mineral collector and dealer of Cornwall, England.