Scandal! In the vicus, with the anaerobic preservation, orange sandstone tried to pass itself off as Samian pottery.
Hello again everyone! Today was another exciting day on excavation in the vicus, finding fragments of bone, leather, and pottery. Now that we’ve been here a few weeks, us first time excavators have learned to recognize the difference between artifacts and rocks! Furthermore, not all the material we find during excavation is worth keeping, and a surprising amount of it is discarded because we cannot gain information from it (for example, twigs that were used to fill a floor). So if you’ll indulge me, we’ll play Archaeological CLUE to find the real artifact hidden among our many suspect materials. Our “room” and “method” will be the vicus trench and anaerobic preservation, so we’ll just need to find the culprit!
Suspect material one is pottery, a common archaeological find. During our first few days working in the North Field at Vindolanda, I struggled with differentiating between red herrings-like rocks and actual pottery. The two cases of mistaken identity were orange sandstone and orange Samian ware pottery, and black pottery and thin black shale. Below are two pictures: what differences do you see?
Pottery and stone are very different materials, so there are some differences that we look for to differentiate between them. First, pottery may have a different visual appearance. Pottery is often smooth and even in size, while rocks are often asymmetrical and of varying thicknesses. Furthermore, pottery often has a curved edge to it that in combination with the other visual cues distinguishes it from rock. But there are other tests too. Pottery has a different texture; while rock is rough and cold, pottery almost feels warm and usually at least one of the sides is smooth. Some archaeologists use taste tests, although that isn’t something we do here. Colour can sometime be used in combination with the other clues, such as for the bright orange, high-quality orange Samian pottery, but you’ll have to be careful not to be misled by colourful rocks.
The second suspect material in this excavation is glass. Glass is a material that continues to be used in the modern era, which makes it a sneaky suspect in shallow trenches that include the plough zone- where layers of archaeology have been mixed together during ploughing and ancient glass may be found alongside modern glass. (When we were in the North Field, we had a real-life example of this when we found lots of Victorian glass, and you can see a beautiful example of ancient glass in the Vindolanda Instagram post about the glass perfume bottle Avery found last week.) There are some clues to look for the distinguish between these characters: modern glass often has fewer bubbles than ancient glass, and modern glass can be much thinner than Roman glass. Ancient glass also has a slight green or blue colour, although this particular clue is used in combination with other features. However, if you are beneath the plough zone and know the ago of other artifacts in the trench, the glass will be from the same period and this step is unnecessary. All the glass we find in the vicus is ancient, because we’re digging through material from 90-105 CE.
Suspect material three is wood. Wood is one of the organic materials that are preserved because of the unique anaerobic conditions at Vindolanda (which means the artifacts are preserved in soil without oxygen). One clue we can use to determine whether we have anaerobic conditions is whether the blue and white iron compound vivianite is present; if it is, anaerobic conditions with high phosphorous concentrations are present. Wood is our most difficult suspect, in that much of the material is discarded because we cannot gain any information from it. Yet every now and then there are pieces worth keeping. Do you think we would keep any of these pieces below?
The types of material that we discard are often ones that have no identifiable purpose, such as off-cuts of wood and rough piece of uneven thickness. For example, wooden posts from rooms are discarded once they have been documented. Small material such as twigs and leaves used to fill floors are searched for other material, and then removed. But, hidden among the rubbish may be even writing or stylus tablets. Writing tablets in particular may contain remnants of ink that we can still read today, and pieces like this we keep because they can give us unique insights into life in the Roman world. (Make sure to check out Garett’s post on writing tablets at Vindolanda). To make wood even harder to classify, small pieces of wood coated in mud may look like bone and need to be carefully checked.
Suspect material four is metal. Metal can be found in coins, moulds, weapons, and jewelry. But metals can be red herrings because they can change colour due to corrosion. Metals like iron often corrode to browns and reds as they form iron oxyhydroxides when exposed to the oxygen in the atmosphere. Many Roman coins consist of brass, an alloy of copper and tin. As such, they can produce green and blue tinged corrosion around them. Lead and zinc both leave white corrosion. Conversely, coins that have been preserved in anaerobic conditions are often not corroded and will retain their original colours; primarily yellow for brass coins. Just like in CLUE, we need to know not just the suspect, but the location and the weapon: in this case, the material, the location, and the conditions of preservation. Between our red rust, orange Samian, yellow brass coins, green corroded copper alloy, blue vivianite, and black soil, we have a rainbow of colours to work through when looking for clues for our real artifact.
There are some totally innocent bystanders in our archaeological game. Leather, bones, and metal nails are so distinct that they rarely have a case of mistaken identity. Likewise, large wooden posts that are too big to be hiding as writing tablets are hard to mistake, and can be discarded if the excavation is proceeding to a lower level and the posts have been recorded.
I hope you have enjoyed this brief introduction to finding and assessing archaeological artifacts. Now I hope you’re ready to play archaeological clue. Can you pick out the guilty subjects that are actual Roman artefacts that modern archaeologists would keep? Can you spot the pot? Good luck! (I’ll post the answers tomorrow).
Round one: wood with streaks of vivianite. Is this an artifact worth keeping?
Round two: a piece of quartz. Is this an archaeological artifact?
Round three: pottery or rock?