On Type Romarchite and Hydroromarchite From Boundary Falls, Ontario, and Notes on Other Occurrences

Abstract

The type material of romarchite and hydroromarchite from Boundary Falls, Winnipeg River, Ontario, Canada, was re-examined. The minerals form deposits on pewter bowls and are products of tin corrosion in a unique cold freshwater environment. Type romarchite is very fine-grained and replaces pseudotetragonal crystals of an unknown precursor. Revised X-ray powderdiffraction data are consistent with the accepted tetragonal symmetry and space group P4/nmm, and provide the refined unit-cell parameters a 3.8014(3), c 4.8559(6) Å. Type hydroromarchite forms euhedral single crystals. Revised X-ray powder-diffraction data are consistent with the accepted tetragonal symmetry and space group P42 1 c, and provide the refined unit-cell parameters a 7.9269(5), c 9.0970(9) Å. Additional Sn-bearing corrosion products are SnO 2 (cassiterite) and two unidentified phases. Residual aggregates of Pb, SbSn and Cu 6 Sn 5 (-bronze) are found in areas of deep localized corrosion. Reports of romarchite subsequent to the original description are numerous, but those of hydroromarchite are few and only quite recent. SOMMAIRENous avons ré-examiné les échantillons holotypes de la romarchite et de l'hydroromarchite provenant des chutes Boundary, sur la rivière Winnipeg, en Ontario, Canada. Ces minéraux se sont formés sur des bols enfouis en étain comme produits de la corrosion de l'étain dans un milieu unique d'eau fraîche froide. Le romarchite type a une granulométrie très fine et remplace des cristaux pseudotétragonaux d'un précurseur méconnu. Les données révisées obtenues en diffraction X, méthode des poudres, concordent avec la symétrie tétragonale acceptée et le groupe spatial P4/nmm, et mènent aux paramètres réticulaires affinés a 3.8014(3), c 4.8559(6) Å. L'hydroromarchite type forme des monocristaux idiomorphes. Les données révisées en diffraction X, méthode des poudres, concordent avec la symétrie tétragonale acceptée et le groupe spatial P42 1 c, et mènent aux paramètres réticulaires a 7.9269(5), c 9.0970(9) Å. Sont aussi présents comme produits de corrosion stannifères SnO 2 (cassitérite) et deux phases non identifiées. Des aggrégats résiduels de Pb, SbSn et Cu 6 Sn 5 (bronze-) ont été décelés dans des endroits où la corrosion était accentuée. Les indices de romarchite connus depuis sa découverte sont nombreux, mais ceux de la hydroromarchite sont peu nombreux et assez récents.(Traduit par la Rédaction) Mots-clés: romarchite, hydroromarchite, oxyde d'étain, étain, produit de corrosion, données en diffraction X, chute Boundary, Ontario, Canada. § E-mail address: bobr@rom.on.ca 650 THE CANADIAN MINERALOGIST tions of romarchite and hydroromarchite (gram and milligram quantities, respectively) on the two bowls registered under M28744 in the ROM mineral collections are designated holotypes. A considerable quantity of romarchite is also present on the bowl registered under M49593.

THE STRUCTURES OF TWO NOVEL Sn2+ OXYSALTS FOUND WITH ROMARCHITE AND HYDROROMARCHITE AS CORROSION PRODUCTS OF PEWTER ARTIFACTS

“…Černý et al (1988) reviewed the occurrence of divalenttin minerals in granitic pegmatites, and concluded that conditions of exceptionally low oxygen fugacity are required for their formation. Abhurite, hydroromarchite and romarchite generally have an anthropogenic origin, being derived from the corrosion of tin, bronze, or pewter artifacts (Ramik et al 2003), commonly in a marine environment, e.g., relics on sunken ships (Dunkle et al 2003(Dunkle et al , 2004. Rarely, romarchite occurs as a natural (non-anthropogenic) product from the alteration of native tin, or as a replacement of the tin sulfi de herzenbergite (cf.…”

“…Rarely, romarchite occurs as a natural (non-anthropogenic) product from the alteration of native tin, or as a replacement of the tin sulfi de herzenbergite (cf. Ramik et al 2003). In the type material, romarchite occurs as a fi ne-grained black pseudomorph after a lower-symmetry species (Ramik et al 2003); the precursor is likely to have been the metastable orthorhombic polymorph of romarchite, red stannous oxide (cf.…”

“…Ramik et al 2003). In the type material, romarchite occurs as a fi ne-grained black pseudomorph after a lower-symmetry species (Ramik et al 2003); the precursor is likely to have been the metastable orthorhombic polymorph of romarchite, red stannous oxide (cf. Donaldson et al 1961, 1963, Donaldson 1964.…”

“…Natural hydroromarchite has been reported to occur in massive sphalerite-pyrite ore at the Corchia mine, western Emilia Romagna, Italy (Garuti & Zaccarini 2005). Ramik et al (2003) described two unknown tinbearing phases (UTP-1 and UTP-2) that occur with type material of romarchite and hydroromarchite; for the two unknowns, they listed the strongest reflections of their powder X-ray-diffraction patterns and presented SEM images. We have determined the structures of these phases: UTP-1 is a novel Sn 2+ sulfate, Sn 6 O 4 (SO 4 )(OH) 2 , which occurs as thin white plates, and UTP-2 is a novel Sn 2+ silicate, Sn 6 O 4 (SiO 4 ), which occurs as stubby yellow hexagonal prisms.…”

“…Along with romarchite and hydroromarchite, these stannous compounds resulted from the corrosion of pewter bowls in fi ve meters of cold freshwater. The bowls had been lost for approximately 160 years below the rapids at Boundary Falls, on the Winnipeg River, Kenora District, Ontario, at latitude 50°13'15"N, longitude 95°06'12"W (Ramik et al 2003). The Commission on New Minerals and Mineral Names (CNMMN) of the International Mineralogical Association approved two of the corrosion products as the new mineral species romarchite and hydroromarchite in 1969 despite their anthropogenic origin (Organ & Mandarino 1971, Ramik et al 2003.…”