Then there were the pieces of galena and "lead slag" from the site of La Isabela, the short-lived settlement (1494-1498) of the second expedition of Columbus to the New World.  I identified the supposed slag as residues of cupellation, and had worked out a very nice little story in which Columbus had being prospecting for silver in the Caribbean but had decided not to tell his royal patrons (Ferdinand and Isabela) about his finds.  To find out which of the Caribbean lead deposits he had sampled. I enlisted a graduate student, Alyson Thibodeau, to run lead isotopes on the galenas. This saved me from making a terrible blunder, as the lead isotopes clearly showed that the galena came from Spain, not from any island in the Caribbean!  Marcos Martinon-Torres suggested that the galena was brought to La Isabela from Spain as a chemical reagent, and we came up with a plausible (to us, anyway) explanation, which was that the last desperate members of the expedition had broken into the royal storehouse, and had assumed the same as I had - that the galena was rich silver ore that Columbus had been hiding from them!  (Thibodeau, A.M., D. J. Killick, J Ruiz, J.T. Chesley, K. Deagan, J.-M. Cruxent and W. Lyman, The Strange Case of the Earliest Extraction of Silver by European Colonists in the New World. Proceedings of the National Academy of Sciences 104:3663-366, 2007.)

Perhaps the most bizarre request was from the Arizona Historical Society, whose premises are just a few hundred meters from my lab. Back in 1924 a resident of Tucson brought in to the University of Arizona several cast lead artifacts, many of which have Latin inscriptions on them. (If you Google "Silverbell crosses" you'll find a number of articles on the web about these - the best is the one from the Journal of the Southwest). There was huge interest in these at the time, with some classicists at the University of Arizona accepting them as evidence of a European presence in the American southwest around 800 AD, and others (including O.M. Dalton of the British Museum) rejecting them as crude fakes. An archaeological excavation recovered more of these, all within a hard calcareous deposit that all present (including geologists) took to be caliche (the calcareous layer that is ubiquitous a few inches below surface in the low desert of Arizona). The total assemblage numbers 32 objects, all but one in lead. A couple of years ago I was given slivers cut off five of these and did some electron microprobe analysis with Ken Domanik. All of them have around 2% antimony, the balance being lead. A little research reveals that this alloy was commonly used for the plates in lead-acid batteries in the early 20th century, the antimony being added to prevent the creep that would occur if pure lead were used. So these are an obvious fraud, but whoever carried it out went to a lot of trouble to embed the objects in a calcareous matrix sufficiently like real caliche to fool several geologists. I haven't written anything about this yet.

I just had another oddity come my way.  This one goes back to the circumnavigation of the world by Francis Drake between 1577 and 1580. In 1579 Drake's one surviving ship landed somewhere on the coast of California and left there (according to the undoubtedly genuine account of the expedition) a brass plate with text claiming California for Queen Elizabeth. In 1936 a battered brass plate bearing just such an inscription, said to have been found near San Francisco Bay,  was brought in to Dr Herbert Bolton, a historian at the University of California. He accepted it as genuine and had chemical tests done in 1938 by the metallurgist Cohn Fink at Columbia University, who thought it genuine.  In 1975 it was reexamined by Cyril Stanley Smith, whose report can be found here: http://libraries.mit.edu/archives/exhibits/drake/

Smith was skeptical - he thought that the plate had been rolled, which would be an anachronism. But he also suggested that the letters themselves were produced by the use of tracers, chasers and punches of the type usually used by silversmiths.  Fast forward to last week, when I was contacted by a person in California who claims to have discovered a set of iron tracing tools within 150 yards of the location of the spot where the brass plate was found.  The binder that he sent me contains only photographs of the 21 heavily corroded circular tracing tools and a rod, which he interprets as a handle for the tools.  I know nothing about chasing tools, but what drew my eye were the two chemical analyses (done in 2002 and 2003) of sample tools, each of which contains 1.0% Mn.  I deduce from this that the iron must date after Robert Mushet's first use in the late 1850's of spiegeleisen (Fe/Mn/C alloy) to solve the problems encountered by early users of the Bessemer process. (If anyone knows of iron with 1% Mn before this date, please tell me). With my present information, therefore, I think that this is probably a late 19th-century set of tools.

And the brass plate?  In 2003 Frank Asaro and Helen Michael (names well known to archaeometrists of a certain age) showed that the brass plate has 35% Zn - which Asaro and Michael claimed to be too high for Elizabethan brass. This question was taken up by Mark Pollard and Carl Heron in their Archaeological Chemistry (2nd edition, pp. 209-230). They show that there are in fact a very few pieces of brass of Elizabethan age that have more than 33% Zn, so the Zn content of the purported Drake plate, is not, as Asaro and Michael claimed, definitive proof that it cannot have been the plate left by Drake. More damning are the concerns raised by Cyril Stanley Smith, and the claims by some of Bolton's colleagues that they were just playing a prank on him. (For these you'll have to Google "Drake plate brass").