South African Glass

There are two main areas in sub-Saharan Africa that feature prominently in glass studies: East Africa and South Africa. Unfortunately, there are not very many people looking at glass in sub-Saharan Africa and I haven’t actively searched for material related to sub-Saharan glass in several years, making these entries far less informative than some of my other regional summaries.

More recent research has been done on African glass, and my list is certainly not exhaustive, but I know of three main published sources for South African glass studies.  One looks at beads form Mapungubwe and Bambandyanolo in the Limpopo Valley of South Africa and Zimbabwe, Zimbabwe.  The second looks at beads specifically from Mapungubwe, and the third looks at sites from Botswana, South Africa, and Zimbabwe.

The Objects

All three studies focus specifically on glass beads.  My understanding is that beads form the primary body of glass material from this region.

Distribution

Davison 1972 analyzes the chemical compositions of glass beads from Mapungubwe and Bambandyanalo (K2?) in the Limpopo Valley of South Africa as well as those from Zimbabwe, Zimbabwe. Prinsloo and Colomban 2008 focus on beads from Mapungubwe, South Africa.  Robertshaw et al 2010 analyze beads from various sites in Botswana, South Africa, and Zimbabwe.

The three main sites in Davison 1972 date to between the eleventh and fourteenth centuries.  Dussubieux et al 2008 look at beads from two different chronologies. Prinsloo and Colomban 2008 look at beads from around 1000-1300 AD.  Sites analyzed by Robertshaw et al 2010 date between the 8th and 16th centuries AD.  Similar to studies from East Africa, the beads themselves generally come from contexts dating much later than those in Asia or Europe.

Technology

All studies discuss wound and drawn beads, but evidence for manufacture is rare.  Davison mentions that moulded beads are rare in Southern Africa.

Chemistry

Interestingly, Davison has identified a Mapungubwe chemical group (a m-Na-Ca subtype) and an M1 group found in Bambandyanalo.  Others identify glass at Mapungubwe as being a plant ash soda-lime glass rather than mineral soda-lime (v-Na-Ca, not m-Na-Ca), and link it to glass from Egypt and the Middle East.  Robertshaw also identifies a m-Na-Al subtype and the possibility of a v-Na-Ca-Al variety, but it’s a bit uncertain in the sources I have.

Social Structure

As with East Africa, there is not enough accessible research for me to make many comments on social structure.  Some of the chemical types mentioned seem fairly distinct, suggesting the possibility of manufacture or at least recycling, but I don’t know of any direct evidence for manufacture in the area.

We do see a connection to South and Southeast Asia in these materials, particularly in the identification of m-Na-Al glasses.  There is also a possible connection to the Middle East through the m-Na-Ca and v-Na-Ca glasses.  Some sources suggest European connections, which are understandable, given that many of these beads come from contexts dating to the time of European exploration.

Regarding the different sources, it seems that there is a shift from using objects that are probably Middle Eastern in origin to objects that are probably South Asian.  That is, these chemical types and geographical connections we see are not necessarily all happening at once, but may be occurring to different degrees at different times.

References

Davison, Claire C.
1972    Glass Beads in African Archaeology: Results of Neutron Activation Analysis, Supplemented by Results of X-Ray Flourescence Analysis.

Prinsloo, Linda C and Phillipe Colomban
2008    A Raman spectroscopic study of the Mapungubwe oblates: glass trade beads excavated at an Iron Age archaeological site in South Africa.  Journal of Raman Spetroscopy 39:79-90.

Robertshaw, Peter, Marilee Wood, Erik Melchiorre, Rachel S. Popelka-Filcoff, and Michael D. Glascock
2010    Southern African glass beads: chemistry, glass sources, and patterns of trade.  Journal of Archaeological Science xxx(2010): 1 – 15.

 

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Bead Materials

Beads can be made from a wide range of materials, from glass to plastic to shell to painted macaroni.  Here’s a list of materials of beads we find in the archaeological record:

Glass – Glass is the main type of bead we find, partly because once people knew how to make glass, they could make far more beads far easier from glass than they could from amethyst or shell or other materials.  Glass also generally has a wider variety of colours and doesn’t break very easily when in bead form.  If an object has air bubbles, it is most likely glass.  Glass also tends to be fairly dense and therefore heavier, but there are certain stones and metals that are heavier than glass.  You can also look for signs that the material was once plastic – tendrils coming off of the object or the sense that it is a liquid frozen in solid form.

Glass beads from the Philippines

Glass beads from the Philippines

Stone – This can be gemstones (e.g. amethyst, carnelian, agate, jade, etc) or other stones (e.g. soapstone or sandstone).  Gemstones are far more frequently used to manufacture beads, due to their aesthetic quality and value.  In the archaeological record, the stone beads we most commonly deal with are made from agate, carnelian, amethyst, garnet, or rock crystal.  Stone beads are often marbled in colour and tend to be heavier than many other materials.  They are also often more chipped than glass tends to be, due to the nature in which they are made.

Carnelian beads from Cebu, Philippines

Carnelian beads from Cebu, Philippines

Metal - Metals, particularly precious metals (e.g. gold and silver) are fairly common materials for beads (see the photo above for some gold beads).  We also see metals combined with other materials to make beads, something we don’t usually see with other materials.  Metal foil glass beads or stone or glass beads capped with metal are good examples of this.  Metals are usually shiny, cool to the touch, good conductors of heat, and sometimes magnetic.  Metals are often corroded in the archaeological record, so the shiny factor is often unhelpful, but corroded metals are often rusty orange or green in colour.

Amber – Amber is fossilised tree resin (not sap) from several now extinct species of pine tree.  Its distribution is limited, and so its use in the ancient world is not nearly as prevalent as stone or glass.  I have seen amber used most prevalently in European contexts, where sizeable deposits can be found.  Amber is often a distinctive mottled orange/red/yellow colour, and shining a light through it shows a crackling effect.

Amber bead from Orkney, Scotland

Amber bead from Orkney, Scotland lit from behind)

Amber bead from Orkney, Scotland lit from behind)

Jet - There are two forms of jet, one formed through high pressure decomposition of wood in salt water (hard jet) and the other through high pressure decomposition of wood in fresh water (soft jet).  Jet was used in jewellery primarily from the Neolithic through the end of the Roman period, but spans all periods in the archaeological record.  To distinguish between jet and opaque black glass, hold the object in your hand.  Jet is very light (since it’s less dense than glass) and not cool to the touch.  Black glass is heavier (denser) and cool to the touch.

Bone – Certain beads are made from bone, usually from animals.  I am including teeth and ivory in there, since the material is similar.  Bone is usually white or a very light colour and porous or spongy.  Bone is also incredibly light in weight.  Archaeologists also often test materials using their tongue – the spongy nature of bone causes it to stick, whereas stone and other materials won’t.  Note: Archaeologists merely touch the object to their tongue, usually when they can’t tell the material by sight.  We don’t go around licking everything!

Shell – Shell has been used for beads for many millennia.  They can be used whole or cut into shapes, and both styles have holes either drilled or rubbed into them. Shell is soft enough that rubbing on a stone will eventually create a hole.  Drilling will probably work faster, but runs a much higher risk of breaking the shell.  Whole shells should be easy enough to identify, while cut shells can be distinguished by the thin, hard, and often shiny nature of the material along with its light weight.

Ceramic - Ceramic beads are common, and many of us have made beads out of clay as children.  You can usually see the original earthy nature of the material, and ceramics also stick to your tongue if you want to be sure.  Ceramics are usually heavier than bone or shell, but lighter than stone or glass.

 

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Bead Bias: Looking at Materials Besides Glass

Not many people look at beads in the archaeological record.  Very few look at beads in archaeological assemblages in Britain.  Of the people who look at beads, though, the vast majority look at beads made of glass.

I love glass beads.  I adore them.  You should see me when someone hands me a bead – I honestly freak out.  My friends have said that they need to give me a chill pill before handing me a bead, because I get way too excited.

I love glass beads.

But I also love other beads.  Beads rock.  I don’t really care what they’re made of – glass, amber, rock crystal, agate, carnelian, jade, jet, amethyst, shell, bone, terracotta, whatever.  Beads are awesome. Period.

But there’s a bit of a bias in archaeology in terms of the literature associated with beads.  The largest body of research looks at glass beads.  There is also a sizable amount of work on stone beads, though much of that focuses on South, Southeast, and East Asian material.  I don’t think I’ve seen anything looking at stone beads in Europe, but I also haven’t spent huge amounts of time looking.  Also, when it comes to stone beads, most work has centred on agate and carnelian beads and not so much any other type of stone.

There is virtually no literature looking at amber beads.  There is almost nothing on shell beads.  Or bone.  Or terracotta.

This doesn’t mean there isn’t any research done on these beads, but the literature is severely lacking.

Also, when beads like amber or rock crystal or shell appear in the literature, they are usually mentioned only in terms of how many there are: “eight amber beads were found” or “a few beads of rock crystal were recovered.”  With glass or carnelian or agate, there is at least the general tendency to speak of colour or shape, whereas these other materials are only mentioned.  Even in studies where amber beads make up over half of the data, they are still not examined in detail – only the number of amber beads at each site is given.

But beads of these materials differ amongst themselves in shape and colour, just as glass and agate and carnelian beads do.  Granted, glass has a very wide range of potential colours, but that doesn’t make the colour range of rock crystal or carnelian any less interesting or potentially important.

Bead studies in archaeology needs more people studying beads.  But we also need more people studying a wider variety of materials, and we need bead specialists to be literate in more than one material.   Glass is cool, but so are all these other materials being used.  And the variety of material used in the past begs the question: if we only limit ourselves to one material of beads, then can we really come to an understanding of that type of object in the past?

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Branching Out from Archaeology

Archaeologists often pride themselves in being interdisciplinary.  We study objects, landscape, geology, environmental science, biological science, chemistry, art, history, craft production, literature, physics, philosophy, agriculture, husbandry, and the list can honestly go on and on and on.

One thing we don’t do so well with is admitting that a non-archaeologist may have valuable insight into our problem. Continue reading

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Glass Chemistry Cheat Sheet

glass chem

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The Chemical-Visual Divide in Bead Archaeology

Last week I wrote a post about issues with bead reporting.  One of the steps I suggested for improving our current system was for bead specialists to stop dividing themselves into those who look at chemical analysis and those who look at essentially everything else (what I’m calling visual characteristics).  Since very few people reading this post are familiar with the issue, I figured I would explain it in a bit more detail. Continue reading

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The Chaos of Bead Reporting

Beads are incredibly common in the archaeological record and date back well into the Neolithic if not before.  Shell, bone, amber, stone, glass, clay, and metal have all been turned into beads over the millennia and they appear at far more sites than you might think.  I know of at least 140 sites in Anglo-Saxon period England with glass beads alone.

Beads are everywhere. Continue reading

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Visual Classification of Beads

Beads come in all shapes, sizes, colours, and materials.  They can be manufactured in a number of ways and have any combination of decorations and alterations to their form.  So few people study glass beads that there is no standard method for discussing or classifying them.  Continue reading

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3D Modeling and Bead Studies

Last night I attended a lecture by Stuart Jeffrey from the Glasgow School of Art about the digital modeling of archaeological sites, structures, and artefacts.  Using various technologies (often but not always involving lasers), we can create 3D models of an object and then (in the case of artefacts) use a 3D printer to make a replica. Continue reading

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Chemical Issues

In order for chemical analysis of glass to really work in terms of sourcing where the glass is coming from, we have to assume that each glass-making workshop has its own unique chemical signature.  Otherwise, we can’t use chemistry to source the glass. Continue reading

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