Found on the Beach ....

.. but what does it mean?

On 05/11/11 2:41 PM, Peter  wrote:

I'm writing to you to see if you or someone you know might be able to help me identify some items I found while walking along a beach on Cape Cod in Massachusetts. At the base of an eroding bank on a marine estuary with direct access to the ocean, I found what appears to be bloomery slag and a stone that might be a bellows shield stone.

Image by Peter Hosmer

First - remember the long history of European occupation in that area. Likely to the early 1600's, I'd think 1650 for certain.
Many of the earliest colony attempts by the English had a 'make it pay' set up. Iron smelting was one of the potential money making enterprises often attempted at many colonies.
Add to this the explosion of small bloomery furnaces all over the Colonies just after the Revolution. This to supply raw iron after the Americans cut themselves off from English industrial supplies! Many of these furnace operations used locally available primary bog ore, which is a resource quickly depleted. This, plus the huge amount of charcoal required, caused many of this kind of small operation to be relatively short lived.

The stone has a hole chiseled in the center and is about 18" long and 10" wide and 2" thick.

Image by Peter Hosmer

If this was in fact a bellows shield stone, one side would quite obviously be subjected to extremely high temperatures. There should be cracking and obvious discolouration. Depending on rock type, the stone itself might be physically melted. You might even find bits of slag attached to the stone. If both sides have the same appearance as shown in your photo - none of these effects are seen. It is very unlikely this stone has been exposed to the 1100 C plus temperatures created in a working charcoal forge.

Remember that side blast forges for charcoal were in common use up through the Colonial period into the early Industrial. Depending on just were you are located, suitable coal for forge work (a specific type and quality required) might not be available. Coastal locations often had coal shipped in from England. (See Revolution effect again). Until canals / rail systems are established, many locations were forced back to charcoal fuel. So even if this stone shows heat effects, it could easily be Colonial activities.

Although you did not expressly state 'Viking Age', I wonder if you were considering this?
Remember there is absolutely *no* physical archaeological evidence of Norse activities further south than central New Brunswick (and that most likely on the Bay of St Lawrence side). (Note that the 'Maine Penny' is held as a chance find - likely via First Nations' internal trade.)  See this article by Dr Birgitta Wallace

The slag varies in size and appearance, and some pieces have shell fragments embedded in them. There is a relatively small amount of slag - perhaps a small pail full and over the course of the last 8 - 10 months could be seen emerging from the embankment as erosion took it's toll.

Image by Peter Hosmer

So - it is clear that the material is coming from the bank - not washed up out of the water? 

Slag is produced from other high temperature activities, but the colour certainly suggests iron smelting slag. The dark colour indicates the presence of iron, as does the fluid shape of the pieces. 

The shell fragments suggest a furnace set at natural ground level, this and the shape of the flow, from a slag tapping type. That type of furnace (as above) was used up to the 1800's at least, especially for small scale operations. What is the change in shore line at your location over the last 200 - 400 years? 

The small amount suggests a small furnace - but you can not tell if you are just getting the first edges of a larger field.

Remember that there is a 'rough' balance in an iron smelting furnace : 

Ore IN = Slag + Iron OUT

Now, this is pretty rough in an actual working furnace. Another consideration is yield, which is most directly modified by the iron content of the ore (but also relative furnace size, experience of the iron master, total size of the smelt itself). This all is going to effect how much slag is going to be left over from a given smelt attempt. Any way you look at it, the slag amount should be in the range of tens of kilograms. Much more than your photograph suggests.

If you really want to nail the potential dates, the shell fragments might be carbon dated. This would not be definitive, but might give you a kind of 'no older than' type of date.

I would first suggest checking local records and history to see if there is any record of Colonial iron smelting activities. Such are usually noted, both as 'proof of progress' in a settlement - but also because such operations usually were taxed as well!

As Regular Readers know, I often take this kind of request and turn it into a blog posting. Be Warned!

(In fact, it was the time I was spending on this type of information that lead me to start this blog in the first place.) If you want to know more about the mechanics of contacting me for a personal research request such as this, check the 'fine print' published on the web site.