Personal adornments are considered one of the key cultural traits of Modern Humans, and appear to have been more-or-less ubiquitous in all Human societies for at least the past 40 000 years. Adornments are used to convey information about an individuals social status, beliefs, gender identity, kinship, and affiliations, as well as personal taste, with these symbols typically being recognizable to other members of the society in which they live. Early adornments, in the form of perforated shells presumed to have been strung together as beads, appear in Africa north and south of the Sahara, as well as parts of the Middle East from about 82 000 years ago, with possible earlier use by the Aterian Culture of North Africa as long as 130 000 years ago (claims have been made for beads older than this, although these are not generally accepted anymore).
However, while there is strong evidence for these ancient items having been beads, with examples such as shells from Blombos Cave in South Africa, which show signs both of having sustained wear while hanging on a string, and of having been painted with red ochre, there is a gap in the archaeological record between about 70 000 and 450 0000 years ago, during which no beads are known, followed by a sudden re-appearance of beads, and their spreading to every inhabited landmass by about 40 000 years ago. These later beads are no longer made exclusively of shell, with bone and stone also being used as bead-making materials, and the appearance of pendants as well as simple strings of beads, and evidence that beads were being traded over quite long distances, at least in Southern Africa.
By the middle of first millennium BC, semi-precious stones were being widely used to make beads, and traded over wide areas, with examples having been used to demonstrate trade links between West and East Africa, the Indian Ocean rim, and Europe. However, while these high-status items appear to have been traded over wide areas, many people were still using beads made from local materials, with examples of locally-produced-and-used beads from Africa including the jasper beads known from Niger, a variety of stone and mineral beads from around Lake Turkana, in Kenya, and the stone beads of Njoro River Cave, also in Kenya.
Talc, talc-schist, soapstone, and steatite, are soft rocks easily carved into beads or other items, found widely in sub-Saharan Africa. Despite this, beads made from these materials are somewhat unusual on the continent. Talc is the softest of these minerals, and with a rating of 1 on the Mohs scale, is generally rated the softest mineral of any kind. It is variable in colour, ranging from white to green, depending on the nature and position of the metal ions within its crystal structure. Furthermore, while it's softness makes it easy to carve, it can be hardened by heating, reaching 3-5 on on the Mohs scale when heated to above 800°C and as much as 7 (equivalent to quartz) when heated to above 1000°C.
Talk which had apparently been collected with the intention of manufacturing something has been recovered from the Iron Age Thaba ya Batswana archaeological site, a stone walled enclosure to the south of Johannesburg, thought to date to about 1700 AD. Talk and soapstone were also utilized by early herders in East Africa to make beads and pendants. Away from Africa, soapstone items were widely used to make personal adornments in the Near East during the Neolithic, with items known from sites such as Çatalhöyük in Turkey, and Abu Hureyra, Tell Aswad, Dja’de el-Mughara, and Tell Halula, all in Syria, as well as sites in Israel, as well as and several Upper Palaeolithic Aurignacian sites from France, several sites associated with the Indus Valley Civilization in northern India, dated to between the 5th and 2nd millennia BC, the 10 000-year-old Arch Lake human burial site in New Mexico, and 15-16th century AD sites in eastern North America.
In a paper published in the journal Archaeological and Anthropological Sciences on 7 February 2023, Mafalda Costa of the HERCULES Laboratory at the University of Évora, and the Archaeometry Research Group at Ghent University, Pedro Barrulas, also of the HERCULES Laboratory at the University of Évora, Maria da Conceição Lopes of the Research Center in Archaeology and the Department of History, Archaeology and Arts at the University of Coimbra, João Barreira, also of the Research Center in Archaeology at the University of Coimbra, Maria da Piedade de Jesus of the Angolan Instituto Nacional Do Património Cultural, Sónia da Silva Domingos of the Angolan Centro Nacional de Investigação Científc, Peter Vandenabeele, also of the Archaeometry Research Group, and of the Raman Spectroscopy Research Group, at Ghent University, José Mirão, also of the HERCULES Laboratory, and of the Department of Geosciences at the University of Évora, present the results of a chemical and mineralogical characterization of a broken mustard-gold-colored stone bead excavated from the Lumbu archaeological site within Mbanza Kongo, the pre-colonial capitol of the Kongo Kingdom, which covered much of what if now northern Angola and the west of the Democratic Republic of Kongo between the thirteenth and nineteenth centuries AD.
The Kongo Kingdom is considered to have been highly socially stratified and centralized society prior to its first contact with Portuguese explorers in 1483. The Portuguese introduced Christianity to the nation, as well as a range of new technologies, and integrated it into a transatlantic trade network. The capital of this kingdom, Mbanza Kongo, was founded in the mid fourteenth century, and is considered to be the oldest continuously occupies settlement in West Central Africa, today being the capital of Zaire Province in northwest Angola. The Lumba archaeological site, uncovered during a three-month archaeological site in 2014, is thought to have either been a royal residence or a ceremonial court. The site comprises a dry-stone building made from irregularly shaped blocks, arranged in an uneven fashion, which led to the walls having considerable variation in thickness. Two radiocarbon dates have been obtained from pieces of charcoal from different parts of the site, these being 1637 and 1950.
The 2014 excavations produced a range of ceramic vessels, including Portuguese-made pottery, fragments of clay pottery, and a total of 53 beads, 52 of which were glass 'trade-beads' of European manufacture, but one, identified as 'Type 44' is a broken mustard-gold-colored bead, made from a softer material, initially thought to be clay. The surviving bead-fragment is about 8.7 mm in width, 9.0 mm long, and has a maximum thickness of 8.9 mm, with a central perforation with a maximum diameter of 5.6 mm. The unbroken end is rounded, possibly by contact with other beads on a string. In form, the bead resembles a monochrome elongate glass bead. It was found in Stratigraphic Unit 6 of area H17 at Lumba, along with several hexagonal blue glass beads made in Bohemia in the nineteenth century, and some blue and green glass beads thought to be of Venetian manufacture.
Examination of Type 44 under a stereomicroscope revealed it was made from a fine-grained material, with white, black, and dark brown mineral inclusions. The fine grains were found to be made from platy grains of magnesium silicate with a maximum size of 10 µm, making the substance talc. The mineral inclusions range from 5 to 30 µm in size, and appear to be a mixture of zircons, iron oxides, and iron-titanium oxides. During the examination, the bead was accidentally scratched with a fingernail, suggesting it has a hardness of about 2.5 on the Mohs scale. This could be consistent with a talc bead which has been heat-treated to harden it although mineral inclusions can also harden talc this much.
Trace element, and rare earth element, analysis has been used to distinguish talc-minerals from different environments. Talc which formed in marine environments tend to be more enriched in heavier rare earth elements, and depleted in lighter members of the group, as well as having very low levels of cerium and high levels of lanthanum, while talcs from terrestrial hydrothermal systems tend to be enriched in both heavy and light rare earth elements, but deficient in those in the middle of the range. Talcs from ultramafic environments tend to be enriched in chromium and nickel, which often reach levels around 2000 parts per million, while talcs from carbonate environments tend to be very low in these elements.
Type 44 is enriched in heavy rare earth elements, depleted in cerium, and enriched in lanthanum, suggesting that it is made from talc which was precipitated from seawater. The specimen also has a boron concentration typical of seawater, and very low levels of both chromium and nickel, with suggests it formed in a carbonate-rich marine environment, probably with a small amount of detrital material.
Mbanza Kongo sits on rocks of the 575-550-million-year-old Schisto-Calcaire Subgroup, a sequence of sedimentary rocks including of limestones, dolostones, siltstones, and shales with rare intercalations of sandstones, cherts, and evaporites. Two types of talc have been recovered from this sequence, the Pseudo-Oolithe de Kisantu, in which talk oolites are found within quartz-rich layers within a dolomite, and an authigenic hydrothermal talc, which is found associated with copper and lead-zinc mineralizations.
The talc oolites appear to have been formed diagenetically from the remineralization of magnesium-rich clay, and are quite unlike the material from which Type 44 was made. The low levels of chromium and nickel in the material appear to rule out the hydrothermal talc. The talc-schists of Nigeria can also be ruled out as an origin, as these formed within an ultramafic environment. The pattern of rare earth elements and boron concentration seen in the material from which Type 44 is made could support it having been manufactured from an unknown talc-source within the Schisto-Calcaire Subgroup, although such a talc would be likely to have aluminum and iron oxide levels similar to those of the Pseudo-Oolithe de Kisantu, while these are at much higher levels in the Type 44 than in the oolites. However, the Schisto-Calcaire Subgroup outcrops over a wide area in northern Angola, as well as in the vicinity of the Congo River near Luozi, and near Inkisi and Kisantu within the Democratic Republic of Congo, with much of this area, including the area directly around Mbanza Kongo, being very poorly explored by geologists, making it quite possible that unknown talc-deposits within this sequence. Furthermore, the range of materials used in pottery-making in the Kongo Kingdom suggests that the people of the kingdom had a good understanding of the local geology prior to contact with the Portuguese. and even produced talc-rich pottery in the provinces of Nsundi, Mbata, and Mpemba (which is where Mbanza Kongo is located). Since carved talc objects are known from other African kingdoms which were contemporary with Kongo, and likely to have been in contact with it, such as Esie in southwestern Nigeria and Great Zimbabwe in the southeast of modern Zimbabwe, it is quite likely that the people of Kongo had the geological knowledge to seek, locate, and exploit talc resources.
Although Type 44 is only a single (broken) bead, it represents the first known example of a locally made item apparently used for personal adornment. The bead appears to have been made within the Kongo Kingdom, using a source of material familiar to the people of the kingdom, but lost to modern geologists, although it is (obviously) not possible to say quite where this source was. The bead bears a notable resemblance to the elongated monochrome glass beads made in Europe from the sixteenth century onwards, and known to have been exported to the Kongo Kingdom, where glass-making was not known, and appears to represent local craftsmen responding to an introduced European fashion trend.
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