Thibodeau then used lead isotope analysis to determine where La Isabela's galena originated. The ratio of the different forms, or isotopes, of lead provides a kind of fingerprint that can indicate the source of a rock.
"We're looking at something about the rock's chemistry and using that to tell us where it came from," she said. "It's like Antiques Roadshow where the appraiser looks at some characteristic of an antique and says, 'This was made by so-and-so at such-and-such a time.'"
Figuring out that the galena came from Spain led to the question, why bring ore? The documents report that the expedition also brought lead.
By contacting an expert in medieval chemistry, the scientists learned that a common practice of the time was mixing galena with powdered ores suspected of having gold or silver. The process provided an assay of the gold or silver in the newly discovered hunk of ore by comparing it with galena containing a known, small quantity of silver.
Given that the expedition purpose was discovering new sources of precious metals, it makes sense that the members toted along materials to assess their discoveries.
"It was a nice detective story," Killick said. "We think we've solved this one."
But there are more archaeological puzzles out there, Thibodeau said.
"Archaeology tells us what might be an interesting question to ask -- and the physical sciences gives us a way to answer the question," Thibodeau said.
--------------------------------------------------------------------------------
Adapted from materials provided by University of Arizona.
Need to cite this story in your essay, paper, or report? Use one of the following formats:
APA
MLA University of Arizona (2007, February 20).
The Mysterious Case Of Columbus's Silver Ore. ScienceDaily.
Retrieved November 7, 2008, from
http://www.sciencedaily.com /releases/2007/02/070220020756.htm