In the northern Great Lakes region, limestone sediments deposited some 400 million ybp during the Devonian era have experienced erosion, creating karst features such as caves and sinkholes. The groundwater chemical constituents of the shallow seas that produced these rock formations now contribute to the formation of a unique physical (sharp density gradients), chemical (dissolved oxygen-depleted, sulfate-rich) and biological (microbe-dominated) environment in a submerged sinkhole near Middle Island in freshwater Lake Huron. A variety of methods including aerial photography, physico-chemical mapping, time series measurements, remotely operated vehicle (ROV) survey, diver observations and bathymetric mapping were employed to obtain a preliminary understanding of sinkhole features and to observe physical interactions of the system's groundwater with Lake Huron. High conductivity ground water of relatively constant temperature hugs the sinkhole floor creating a distinct sub-ecosystem within this Great Lakes ecosystem. Extensive photosynthetic purple cyanobacterial benthic mats that characterize the benthos of this shallow sinkhole were strictly limited to the zone of ground water influence.

Pewter, a tin-rich alloy, has been widely used for ornamental and utilitarian purposes for the last 400 years because it is durable, relatively easily worked, resistant to corrosion, and similar to silver in appearance. Pewter plates and implements have been recovered and examined from what is believed to be the wreck site of the Queen Anne's Revenge, flagship of the pirate Blackbeard, that sank near Beaufort, North Carolina in 1718. All of the pewter artifacts from the site display a surface veneer of corrosion products and may be viewed as experiments on tin corrosion that have been continuously in operation for more than 280 years. Mineralogical examination of the pewter samples has revealed that the corrosion products are composed of romarchite (SnO), hydroromarchite [Sn 3 O 2 (OH) 2 ], and abhurite [Sn 21 Cl 16 (OH) 14 O 6 ]. 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. Romarchite, hydroromarchite, and abhurite occur as irregular grains and laths up to 100 micrometers in length. Abhurite also occurs as masses of equant grains with abundant small inclusions of residual pewter. Thermodynamic considerations reveal that romarchite may be a metastable phase, and is present as the result of sluggish kinetics in the process of the formation of cassiterite (SnO 2 ), the most stable tin oxide in most natural environments. Observation and identification of these phases will be useful in understanding the stability of tin in the weathering environment and the nature of the metal's corrosion products.Keywords: romarchite, hydroromarchite, abhurite, tin oxide, pewter, corrosion, Queen Anne's Revenge, Blackbeard, metal artifacts, North Carolina. SOMMAIRE L'utilisation d'alliages d'étain a été répandu au cours des 400 dernières années dans les applications ornamentales et utilitaires à cause de leur durabilité, la facilité avec laquelle on peut les travailler, leur résistance à la corrosion, et leur ressemblance à l'argent. Des assiettes et des outils en étain ont été récupérés et examinés d'une épave qui serait celle du Queen Anne's Revenge, navire major du pirate Blackbeard, qui a fait naufrage près de Beaufort, en Caroline du Nord en 1718. Tous les artéfacts en étain provenant de ce site ont un placage de produits de corrosion; on peut ainsi les considérer comme témoins d'une expérience en corrosion de l'étain qui dure depuis plus de 280 ans. Un examen minéralogique de ces échantillons d'étain a révélé la nature de ces produits de corrosion: ils contiennent romarchite (SnO), hydroromarchite [Sn 3 O 2 (OH) 2 ], et abhurite [Sn 21 Cl 16 (OH) 14 O 6 ]. La corrosion se développe en général en couches à peu près concentriques, avec une couche interne d'abhurite en contact avec l'étain; les couches externes contiennent romarchite et hydroromarchite. Romarchite, hydroromarchite, et abhurite se présentent en grains irréguliers et en tablettes atteignant 100 m en longueur....

Corrosion products were examined from typical pewter artifacts originating from six different submerged archaeological sites, dating to between ca. A.D. 1550 and 1733, along the eastern seaboard of North America and in the Caribbean Sea. The artifacts were viewed as 270-450-year long experiments revealing the phases and mechanisms of tin corrosion in seawater. All of the samples analyzed exhibit abhurite (Sn 3 O(OH) 2 Cl 2 ), romarchite (SnO), and hydroromarchite (Sn 3 O 2 (OH) 2 ) forming at the expense of the underlying artifact. Textural analysis suggests that abhurite is the first alteration product to form at the expense of the pewter; romarchite subsequently develops and then hydroromarchite. The outermost corrosion layers on several of the most corroded artifacts also exhibit cassiterite (SnO 2 ) as a significant and apparently final phase to form during alteration. The absence of this mineral on many samples demonstrates that, while samples appeared to be stable under the conditions that were present, cassiterite had not yet had time to form. The very limited stability field for romarchite, based on data presented by Séby et al. (Geochimica et Cosmochimica Acta, 65, 3041-3053, 2001), suggests that its presence on these artifacts may be the result of a kinetic effect. The universal appearance of this mineral on corroding tin suggests that it is a required step in the oxidation of pure tin to the final most stable phase of cassiterite. The stability of romarchite and its effectiveness as an agent of passivation can provide insight into not only the formation of tin oxides but the rate of tin corrosion. This can have significant implications in the field of artifact preservation as well as more widespread industrial applications.

From 1996 investigators of the Beaufort Inlet shipwreck, off North Carolina, USA, have suggested that the remains are those of the Queen Anne's Revenge, flagship of the pirate Blackbeard. Analysis of the published material, however, indicates that no concrete evidence has yet been found to support this identification and, moreover, shows a strong tendency towards Ruling Theory, whereby researchers seem to shape evidence to fit a pre‐conceived identification. This article uses the Beaufort Inlet shipwreck as a case study in the dangers of Ruling Theory and how it can compromise scholarly objectivity, and thwart the generation of useful research questions. It also seeks to demonstrate the benefits of a clear, objective research design for project investigation and management. © 2005 The Nautical Archaeology Society

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