Curse of Oak Island Archaeology Update: The Phips Iron and Lot 5

Season 11 of the Curse of Oak Island (COOI) has featured the finds of iron objects from Lot 5, both because they could be associated with a large pit structure in the same area, and because they are said to be a match, in terms of chemical composition, with iron objects found at the 17th century home of William Phips, further south along the coast in New England.

Phips was British Governor of the Massachusetts Bay Colony in the early 1690s, and in the 1680s was involved in the salvage of what turned out to be a treasure from the wreck of the Nuestra Señora de la Concepción, an admiral vessel of the Spanish Silver Train, lost in 1641.

Portrait of William Phips, from his Wikipedia page

Apparently, actual treasure was actually recovered, although there is disagreement in the sources over how much, and whether Phips and others may have embezzled some of the find. The similarity of the iron found on lot 5 with that found at the Phips home in New England suggests to the COOI team that the Money Pit on Oak Island might contain part of the silver haul from the Concepción. As always with COOI, vague possibility quickly becomes probability.

What is an archaeometallurgical match?

When Emma from the COOI team says that the Lot 5 iron is a chemical, or compositional match to the Phips iron, what does that mean? The composition of archaeological metal is a result of the composition of the ore(s) from which it is extracted, and of the various steps of the extraction and manufacturing process.

Two pieces of iron that are from the same ore and undergo the same transformations are likely to be chemically similar, but that is only meaningful if they are compared at least to a third piece that is different in composition. So it seems the Phips iron is similar in composition to the Lot 5 iron in the context of a broader set of reference material from different times and places.

Because metals are worked and reworked over time, because ores can be mixed, it is always difficult to match metal samples, and it is technically not possible to match them to one particular source. The most one can say is that a particular piece is not likely to be from a particular source, and is likely to be from another.

When comparing objects A, B, and C, for example, one can tell that A and C are much more similar to each other than both of them are to B. Of course, there is always the possibility that there is a fourth source out there that would be very close to A and would suddenly make C look different from A. You can never rule that out.

The methods used to measure the elemental composition of the samples are also important. Different methods have different detection limits for different elements, and some can “see” some elements much better than others. Different methods also have different standard errors for different elements, which can lead to significant overlaps in measurements between samples.

Some of the main methods used in archaeometallurgy include instrumental neutron activation (INAA) and X-ray fluorescence (XRF). INAA has much lower detection limits and error ranges than XRF, but is useful for a narrower range of elements. XRF sees more stuff, but less well, especially for lighter elements. UMass Lowell has a helpful write up on this.

XRF has the advantage over INAA that it doesn’t require a nuclear reactor, which is probably why they use it on the island. It’s also much quicker, requiring minutes rather than weeks. 

From what I can tell, the COOI team use XRF on raw samples (non-destructive analysis) rather than on polished samples or pellets made from powdered samples. That will give you a good sense of the composition, but with some limitations, although I am sure the good people of Nova Scotia will be happy to hear that it helps better preserves their heritage.

Because XRF works by bombarding a surface with energy beams and reading the returns, rough and irregular surfaces scatter the energy and lead to higher detection limits and standard errors than measurements done on polished samples or pellets, making it more difficult to discriminate between samples and to get matches.

What does an archaeometallurgical match mean in this case?

Assuming the match is reasonably good between the Phips iron and the Lot 5 iron, and I have no particular reason to doubt it, that doesn’t indicate, or even strongly suggest a direct link between Phips and the island.

Based on what we see on the show, which isn’t much, I wouldn’t be surprised if the Lot 5 pit structure is in fact a homestead or a cellar from the late 1600s, which is very cool in itself, and doesn’t need to be related to treasure to be archaeologically interesting. It probably dates from around the time of Phips’ life. 

It also corresponds to the period of operation of the Saugus Iron Works in Massachusetts, which produced a variety of iron implements for the Atlantic seaboard from the 1640s to the 1670s. Krysta Ryzewski gives an excellent overview of early colonial metallurgy in New England in her 2008 PhD dissertation at Brown University, including the history of Saugus.

If the Phips Iron and the Lot 5 iron are wholly, or even mostly from Saugus, the match is not surprising at all, since they share a source, both in terms of ore and of manufacturing technique.

There is also the possibility that both are the product of local household production, which used essentially similar techniques throughout early European settlements in the Americas, and produced comparable outputs that would be hard to differentiate from each other with XRF on raw samples. Finished products from Europe might very well show as different, though.

In either case, a match between the Lot 5 iron and the Phips iron, even if it is a very good match chemically (under the circumstances), does not necessarily mean a direct link between Phips and Oak Island, and certainly not between the Money Pit and the treasure of the Concepción. There are plenty of other good reasons for the iron used in the late 1600s on Oak Island and in Massachusetts to be similar.