Simple oxide, anthropogenic
Hardness: 2 to 2½
Romarchite occurs as an alteration product on pewter (tin) objects and is found on veins containing native
At the Maria-Teresa Mine, Huari, Avaroa Province, Oruro, Bolivia, romarchite occurs replacing herzenbergite replacing cassiterite (HOM ).
At the type locality, Boundary Falls, Winnipeg River, Kenora District, Ontario, Canada, romarchite has been found as an alteration product on tin cooking utensils submerged since 1830, associated with hydroromarchite (Mindat, Dana, HOM).
At the Sharm Abhur Cove, Jiddah, Mecca Region, Saudi Arabia, romarchite has been found on tin ingots from the cargo of a ship wrecked in the cove, associated with abhurite, kutnohorite, aragonite and cassiterite (HOM).
At Beaufort, North Carolina, USA, the Queen Anne's Revenge flagship of Blackbeard the pirate sank in 1718. The wreck was discovered in 1996 and pewter artefacts from it were all corroded with corrosion products are 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; the overlying outer layers consist of romarchite and hydroromarchite. All three minerals occur as irregular grains and laths up to 100 micrometers in length, and abhurite also occurs as masses of equant grains with abundant small inclusions of residual pewter (CM 41.649-657).
At the US Virgin Islands, romarchite is abundant in a vein with cassiterite, native tin, copper and lead, and various lead-tin oxides and hydroxides (Dana).
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