Oxide containing hydroxyl, anthropogenic
Hydromarchite generally is of anthropogenic origin by preferential leaching and oxidation of
tin from tin, bronze, or pewter artifacts in a marine or fluvial environment
At the type locality, Boundary Falls, Winnipeg River, Kenora District, Ontario, Canada, hydromarchite occurs as an alteration product on pewter bowls dropped in the river between 1801 and 1821, and is a product of tin corrosion in a unique cold freshwater environment, as is the associated mineral romarchite. Type hydroromarchite forms euhedral single crystals. Additional Sn-bearing corrosion products are cassiterite and two unidentified phases (CM 41.649-657, HOM).
At the Speranza Stope, Corchia mine, Berceto, Parma Province, Emilia-Romagna, Italy, hydromarchite is interstitial in quartz-calcite gangue of a massive sphalerite-pyrite ore body. Associated minerals include siderite, pyrite, smithsonite, sphalerite and baryte (HOM).
The hydroromarchite occurs in massive zinc-iron ore, closely related with late deposition of siderite and secondary pyrite, possibly due to the action of neutral to basic and reducing waters flushing through the ore in the initial stages of seafloor diagenesis (CM 43.935-950).
At the Queen Anne's Revenge wreck site, Beaufort, Carteret county, North Carolina, USA, pewter plates and implements have been recovered and examined from what is believed to be the flagship of the pirate Blackbeard, that sank in 1718. All of the pewter artifacts from the site display a surface veneer of corrosion products composed of romarchite, hydroromarchite and abhurite. The corrosion generally develops in crudely concentric layers, with an inner layer of abhurite in contact with the pewter, and overlying outer layers of romarchite and hydroromarchite. All three minerals occur as irregular grains and laths up to 100 micrometers in length (CM 41.659-669).
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