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Pottery traditions reflect the socioeconomic framework of past cultures, while the spatial distribution of pottery reflects patterns of communication and processes of interaction.Materials and geosciences are employed here to determine the sourcing, selection and processing of raw materials.The Kingdom of the Congo, internationally renowned since the end of the fifteenth century, is one of the most famous ex-colonial states in Central Africa.Although much historical research relies on African and European oral and written chronicles, there are still considerable gaps in our current understanding of this political unit.Here we provide new insights into the production and circulation of pottery in the Kingdom of the Congo.Performing multiple analytical methods on selected samples, namely XRD, TGA, petrographic analysis, XRF, VP-SEM-EDS and ICP-MS, we determined their petrographic, mineralogical and geochemical characteristics.Our results allow us to link archaeological objects with natural materials and establish ceramic traditions.We have identified production templates, exchange patterns, distribution and interaction processes of quality goods through technical knowledge dissemination.Our findings suggest that political centralization in the Lower Congo region of Central Africa has a direct impact on pottery production and circulation.We hope that our study will provide a good basis for further comparative studies to contextualize this region.
The making and use of pottery has been a central activity in many cultures, and its socio-political context has had a major impact on the organization of production and the process of making these objects1,2.Within this framework, ceramic research can enhance our understanding of past societies3,4.By examining archaeological ceramics, we can link their properties to specific ceramic traditions and subsequent patterns of production1,4,5.As pointed out by Matson6, based on ceramic ecology, the choice of raw materials is related to the spatial availability of natural resources.Furthermore, taking into account various ethnographic case studies, Whitbread2 refers to an 84% probability of resource development within a 7km radius of the ceramic origin, compared to an 80% probability within a 3km radius in Africa7.However, it is important not to overlook the dependence of production organizations on technical factors2,3.Technological choices can be investigated by investigating the interrelationships between materials, techniques and technical knowledge3,8,9.A range of such options can define a particular ceramic tradition.At this point, the integration of archaeology into research has contributed significantly to a better understanding of past societies3,10,11,12.The application of multi-analytical methods can address questions about all stages involved in chain operations, such as natural resource development and raw material selection, procurement and processing3,10,11,12.
The study focuses on the Kingdom of Congo, one of the most influential polities to develop in Central Africa.Before the advent of the modern state, Central Africa consisted of a complex socio-political mosaic characterized by large cultural and political differences, with structures ranging from small and fragmented political spheres to complex and highly concentrated political spheres13,14,15.In this socio-political context, the Kingdom of the Congo is thought to have been formed in the 14th century by three adjoining confederations 16, 17.In its heyday, it covered an area roughly equivalent to the area between the Atlantic Ocean to the west of the present-day Democratic Republic of Congo (DRC) and the Cuango River to the east, as well as the area of ​​northern Angola today.Latitude of Luanda.It played a key role in the wider region during its heyday and experienced a development towards greater complexity and centralisation until the 14th, 18th, 19th, 20th, 21st of the eighteenth century.Social stratification, a common currency, taxation systems, specific labor distributions, and the slave trade18, 19 reflect Earle’s model of political economy22.From its founding to the end of the 17th century, the Kingdom of the Congo expanded significantly, and from 1483 onwards established strong ties with Europe, and in this way participated in Atlantic trade 18, 19, 20, 23, 24, 25 (more detailed See Supplement 1) for historical information.
Methods of materials and geosciences have been applied to ceramic artifacts from three archaeological sites in the Kingdom of the Congo, where excavations have been conducted over the past decade, namely Mbanza Kongo in Angola and Kindoki and Ngongo Mbata in the Democratic Republic of Congo (Fig. 1) (see Supplementary Table 1). 2 in the archaeological data).Mbanza Congo, recently inscribed on the UNESCO World Heritage List, is located in the Mpemba province of the ancient regime.Located on a central plateau at the intersection of the most important trade routes, it was the political and administrative capital of the kingdom and the seat of the king’s throne.Kindoki and Ngongo Mbata are located in the provinces of Nsundi and Mbata, respectively, which may have been part of the seven kingdoms of Kongo dia Nlaza before the kingdom was established – one of the combined polities28,29.Both of them played important roles throughout the history of the kingdom17.The archaeological sites of Kindoki and Ngongo Mbata are located in the Inkisi Valley in the northern part of the kingdom and were one of the first areas conquered by the kingdom’s founding fathers.Mbanza Nsundi, the provincial capital with the ruins of Jindoki, has traditionally been ruled by the successors of later Congolese kings 17, 18, 30.Mbata province is mainly located 31 east of the Inkisi River.The rulers of Mbata (and to a certain extent Soyo) have the historical privilege of being the only ones elected from the local nobility by succession, not other provinces where the rulers are appointed by the royal family, which means greater of liquidity 18,26.Although not the provincial capital of Mbata, Ngongo Mbata played a central role at least in the 17th century.Due to its strategic position in the trading network, Ngongo Mbata has contributed to the development of the province as an important trading market16,17,18,26,31,32.
The Kingdom of the Congo and its six main provinces (Mpemba, Nsondi, Mbata, Soyo, Mbamba, Mpangu) in the sixteenth and seventeenth centuries.The three sites discussed in this study (Mbanza Kongo, Kindoki and Ngongo Mbata) are shown on the map.
Until a decade ago, archaeological knowledge of the Kingdom of the Congo was limited33.Most insights into the kingdom’s history are based on local oral traditions and written sources from Africa and Europe16,17.The chronological sequence in the Congo region is fragmented and incomplete due to the lack of systematic archaeological studies34.Archaeological excavations since 2011 have aimed to fill these gaps and have uncovered important structures, features and artifacts.Of these discoveries, potshards is undoubtedly the most important29,30,31,32,35,36.With regard to the Iron Age in Central Africa, archaeological projects like the present are extremely rare37,38.
We present the results of mineralogy, geochemical and petrological analyses of a set of pottery fragments from three excavated areas of the Kingdom of the Congo (see archaeological data in Supplementary Material 2).The samples belonged to four pottery types (Fig. 2), one from the Jindoji Formation and three from the King Kong Formation 30, 31, 35.The Kindoki Group dates back to the Early Kingdom period (14th to mid-15th century).Of the sites discussed in this study, Kindoki (n = 31) was the only site that demonstrated Kindoki grouping30,35.Three types of Kongo Groups – Type A, Type C, and Type D – date back to the late kingdom (16th-18th centuries) and exist simultaneously in the three archaeological sites considered here30, 31, 35.Kongo Type C pots are cooking pots that are abundant in all three locations35.The Kongo A-type pan may be used as a serving pan, represented by only a few fragments 30, 31, 35.Kongo D-type ceramics should only be used for domestic use – as they have never been found in burials to date – and are associated with a specific elite group of users30,31,35.Fragments of them also appear only in small numbers.Type A and D pots showed similar spatial distributions at the Kindoki and Ngongo Mbata sites30,31.In Ngongo Mbata, so far, there are 37,013 Kongo Type C fragments, of which there are only 193 Kongo Type A fragments and 168 Kongo Type D31 fragments.
Illustrations of the four type groups of Congo Kingdom pottery discussed in this study (Kindoki Group and Kongo Group: Types A, C, and D); a graphic representation of their chronological appearance at each archaeological site Mbanza Kongo, Kindoki and Ngongo Mbata .
X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Petrographic Analysis, Variable Pressure Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (VP-SEM-EDS), X-ray Fluorescence Spectroscopy (XRF) and Inductively Coupled Plasma Coupled mass spectrometry (ICP-MS) has been used to address questions about potential sources of raw materials and production techniques.Our aim is to identify ceramic traditions and link them to certain modes of production, thus providing a new perspective on the social structure of one of the most prominent political entities in Central Africa.
The case of the Kingdom of the Congo is particularly challenging for source studies due to the diversity and specificity of the local geological display (Fig. 3).Regional geology can be discerned by the presence of slightly to undeformed geological sedimentary and metamorphic sequences known as the Western Congo Supergroup.In the bottom-up approach, the sequence begins with rhythmically alternating quartzite-claystone formations in the Sansikwa Formation, followed by the Haut Shiloango Formation, characterized by the presence of stromatolite carbonates, and in the Democratic Republic of Congo, silica Diatomaceous earth cells were identified near the bottom and top of the group.The Neoproterozoic Schisto-Calcaire Group is a carbonate-argillite assemblage with some Cu-Pb-Zn mineralization.This geological formation exhibits an unusual process through weak diagenesis of magnesia clay or slight alteration of talc-producing dolomite.This results in the presence of both calcium and talc mineral sources.The unit is covered by the Precambrian Schisto-Greseux Group consisting of sandy-argillaceous red beds.
Geological map of the study area.Three archaeological sites are shown on the map (Mbanza Congo, Jindoki and Ngongombata).The circle around the site represents a radius of 7 km, which corresponds to a source utilization probability of 84%2.The map refers to the Democratic Republic of the Congo and Angola, and the borders are marked.Geological maps (shapefiles in Supplement 11) were created in ArcGIS Pro 2.9.1 software (website: https://www.arcgis.com/), referencing Angolan41 and Congolese42,65 Geological maps (raster files), using Make different drafting standards.
Above the sedimentary discontinuity, Cretaceous units consist of continental sedimentary rocks such as sandstone and claystone.Nearby, this geological formation is known as a secondary depositional source of diamonds after erosion by Early Cretaceous kimberlite tubes41,42.No further igneous and high-grade metamorphic rocks have been reported in this area.
The area around Mbanza Kongo is characterized by the presence of clastic and chemical deposits on Precambrian strata, mainly limestone and dolomite from the Schisto-Calcaire Formation and slate, quartzite and ashwag from the Haut Shiloango Formation41.The closest geological unit to the Jindoji archaeological site is the Holocene alluvial sedimentary rock and limestone, slate and chert covered with feldspar quartzite of the Precambrian Schisto-Greseux Group.Ngongo Mbata is located in a narrow Schisto-Greseux rock belt between the older Schisto-Calcaire Group and the nearby Cretaceous red sandstone42.In addition, a Kimberlite source called Kimpangu has been reported in the wider vicinity of Ngongo Mbata near the craton in the Lower Congo region.
The semi-quantitative results of the main mineral phases obtained by XRD are shown in Table 1, and the representative XRD patterns are shown in Figure 4.Quartz (SiO2) is the main mineral phase, regularly associated with potassium feldspar (KAlSi3O8) and mica.[For example, KAl2(Si3Al)O12(OH)2], and/or talc [Mg3Si4O10(OH)2].The plagioclase minerals [XAl(1–2)Si(3–2)O8, X = Na or Ca] (i.e. sodium and/or anorthite) and amphibole [(X)(0–3)[(Z )(5– 7)(Si, Al)8O22(O,OH,F)2, X = Ca2+, Na+, K+, Z = Mg2+, Fe2+, Fe3+, Mn2+, Al, Ti] are interrelated crystalline phases, Usually there is mica.Amphibole is usually absent from talc.
Representative XRD patterns of Kongo Kingdom pottery, based on major crystalline phases, corresponding to type groups: (i) talc-rich components encountered in the Kindoki Group and Kongo Type C samples, (ii) rich talc encountered in the samples Quartz-containing components Kindoki Group and Kongo Type C samples, (iii) feldspar-rich components in Kongo Type A and Kongo D samples, (iv) mica-rich components in Kongo Type A and Kongo D samples, ( v) Amphibole rich components were encountered in samples from Kongo Type A and Kongo Type D.Q quartz, Pl plagioclase, or potassium feldspar, Am amphibole, Mca mica, Tlc talc, Vrm vermiculite.
The indistinguishable XRD spectra of talc Mg3Si4O10(OH)2 and pyrophyllite Al2Si4O10(OH)2 require a complementary technique to identify their presence, absence or possible coexistence.TGA was performed on three representative samples (MBK_S.14, KDK_S.13 and KDK_S.20).The TG curves (Supplement 3) were consistent with the presence of the talc mineral phase and the absence of pyrophyllite.The dehydroxylation and structural decomposition observed between 850 and 1000 °C correspond to talc.No mass loss was observed between 650 and 850 °C, indicating the absence of pyrophyllite44.
As a minor phase, vermiculite [(Mg, Fe+2, Fe+3)3[(Al, Si)4O10](OH)2 4H2O], determined by analysis of oriented aggregates of representative samples, peak Located at 16-7 Å, mainly detected in Kindoki Group and Kongo Group Type A samples.
Kindoki Group-type samples recovered from the wider area around Kindoki exhibited a mineral composition characterized by the presence of talc, the abundance of quartz and mica, and the presence of potassium feldspar.
The mineral composition of Kongo Type A samples is characterized by the presence of a large number of quartz-mica pairs in varying proportions and the presence of potassium feldspar, plagioclase, amphibole, and mica.The abundance of amphibole and feldspar marks this type group, especially in the Congo-type A samples at Jindoki and Ngongombata.
Kongo Type C samples exhibit a diverse mineral composition within the type group, which is highly dependent on the archaeological site.The samples from Ngongo Mbata are rich in quartz and exhibit a consistent composition.Quartz is also the predominant phase in Kongo C-type samples from Mbanza Kongo and Kindoki, but in these cases some samples are rich in talc and mica.
Kongo type D has a unique mineralogical composition in all three archaeological sites.Feldspar, especially plagioclase, is abundant in this pottery type.Amphibole is usually present in abundance.Represents quartz and mica.The relative amounts vary between samples.Talc was detected in amphibole-rich fragments of the type group Mbanza Kongo.
The main tempered minerals identified by petrographic analysis are quartz, feldspar, mica and amphibole.Rock inclusions consist of fragments of intermediate and high-grade metamorphic, igneous and sedimentary rocks.Fabric data obtained using Orton45′s reference chart shows a state ranking from poor to good, with a ratio of the state matrix from 5% to 50%.Tempered grains range from round to angular with no preferential orientation.
Five lithofacies groups (PGa, PGb, PGc, PGd, and PGe) are distinguished based on structural and mineralogical changes.PGa group: low-specific tempered matrix (5-10%), fine matrix, with large inclusions of sedimentary metamorphic rocks (Fig. 5a); PGb group: high proportion of tempered matrix (20%-30%), tempered matrix The fire sorting is poor, the tempered grains are angular, and the middle and high-grade metamorphic rocks have a high content of layered silicate, mica and large rock inclusions (Fig. 5b); PGc group: relatively high proportion of tempered matrix (20 -40%), good to very good temper sorting, small to very small round tempered grains, abundant quartz grains, occasional planar voids (c in Fig. 5); PGd group: low ratio Tempered matrix (5-20​​​​%), with small tempered grains, large rock inclusions, poor sorting, and fine matrix texture (d in Fig. 5); and PGe group: high proportion of tempered matrix (40-50 %), good to very good temper sorting, two sizes of tempered grains and different mineral compositions in terms of tempering (Fig. 5, e).Figure 5 shows a representative optical micrograph of the petrographic group.Optical studies of the samples led to strong correlations between type classification and petrographic sets, especially in samples from Kindoki and Ngongo Mbata (see Supplementary 4 for representative photomicrographs of the entire sample set).
Representative optical micrographs of Kongo Kingdom pottery slices; correspondence between petrographic and typological groups.(a) PGa group, (b) PGB group, (c) PGc group, (d) PGd group and (e) PGe group.
The Kindoki Formation sample includes well-defined rock formations associated with the PGa formation.The Kongo A-type samples are highly correlated with the PGb lithofacies, except for the Kongo A-type sample NBC_S.4 Kongo-A from Ngongo Mbata, which is related to the PGe group in ordering.Most of the Kongo C-type samples from Kindoki and Ngongo Mbata, and Kongo C-type samples MBK_S.21 and MBK_S.23 from Mbanza Kongo belonged to the PGc group.However, several Kongo Type C samples show features of other lithofacies.Kongo C-type samples MBK_S.17 and NBC_S.13 present texture attributes related to PGe groups.Kongo C-type samples MBK_S.3, MBK_S.12 and MBK_S.14 form a single lithofacies group PGd, while Kongo C-type samples KDK_S.19, KDK_S.20 and KDK_S.25 have similar properties to the PGb group.Kongo Type C sample MBK_S.14 can be considered an outlier due to its porous clast texture.Almost all samples belonging to the Kongo D-type are associated with the PGe lithofacies, except for the Kongo D-type samples MBK_S.7 and MBK_S.15 from Mbanza Kongo, which exhibit larger tempered grains with lower densities (30% ), closer to the PGc group.
Samples from three archaeological sites were analyzed by VP-SEM-EDS to illustrate elemental distribution and to determine the predominant elemental composition of individual tempered grains.EDS data allows identification of quartz, feldspar, amphibole, iron oxides (hematite), titanium oxides (e.g. rutile), titanium iron oxides (ilmenite), zirconium silicates (zircon) and perovskite neosilicates (garnet).Silica, aluminum, potassium, calcium, sodium, titanium, iron and magnesium are the most common chemical elements in the matrix.The consistently high magnesium content in the Kindoki Formation and Kongo A-type basins can be explained by the presence of talc or magnesium clay minerals.According to elemental analysis, the feldspar grains mainly correspond to potassium feldspar, albite, oligoclase, and occasionally labradorite and anorthite (Supplement 5, Fig. S8–S10), while the amphibole grains are tremolite Stone, actinite, in the case of Kongo Type A sample NBC_S.3, red leaf stone.A clear difference is observed in the composition of the amphibole (Fig. 6) in Kongo A-type (tremolite) and Kongo D-type ceramics (actinite).Furthermore, in three archaeological sites, ilmenite grains were closely associated with the D-type samples.High manganese content is found in the ilmenite grains.However, this did not change their common iron-titanium (Fe-Ti) substitution mechanism (see Supplementary 5, Fig. S11).
VP-SEM-EDS data.A ternary diagram illustrating the different composition of amphibole between Kongo Type A and Kongo D tanks on samples selected from Mbanza Kongo (MBK), Kindoki (KDK), and Ngongo Mbata (NBC); symbols encoded by type groups.
According to the XRD results, quartz and potassium feldspar are the main minerals in Kongo type C samples, while the presence of quartz, potassium feldspar, albite, anorthite and tremolite are characteristic of Kongo type A samples.Kongo D-type samples show that quartz, potassium feldspar, albite, oligofeldspar, ilmenite and actinite are the main mineral components.Kongo type A sample NBC_S.3 can be considered an outlier because its plagioclase is labradorite, amphibole is orthopamphibole, and the presence of ilmenite is recorded.Kongo C-type sample NBC_S.14 also contains ilmenite grains (Supplementary 5, Figures S12–S15).
XRF analysis was performed on representative samples from three archaeological sites to determine major element groups.The main element compositions are listed in Table 2.The analyzed samples were shown to be rich in silica and alumina, with calcium oxide concentrations below 6%.The high concentration of magnesium is attributed to the presence of talc, which is inversely related to oxides of silicon and aluminum oxide.The higher sodium oxide and calcium oxide contents are consistent with the abundance of plagioclase.
Kindoki Group samples recovered from the Kindoki site showed significant enrichment of magnesia (8-10%) due to the presence of talc.Potassium oxide levels in this type group ranged from 1.5 to 2.5%, and sodium (< 0.2%) and calcium oxide (< 0.4%) concentrations were lower.
High concentrations of iron oxides (7.5–9%) are a common feature of Kongo A-type pots.Kongo type A samples from Mbanza Kongo and Kindoki showed higher concentrations of potassium (3.5–4.5%).The high magnesium oxide content (3–5%) distinguishes the Ngongo Mbata sample from other samples of the same type group.Kongo type A sample NBC_S.4 exhibits very high concentrations of iron oxides, which are associated with the presence of amphibole mineral phases.Kongo type A sample NBC_S.3 showed high manganese concentration (1.25%).
Silica (60-70%) dominates the composition of the Kongo C-type sample, which is inherent to the quartz content determined by XRD and petrography.Low sodium (< 0.5%) and calcium (0.2–0.6%) contents were observed.Higher concentrations of magnesium oxide (13.9 and 20.7%, respectively) and lower iron oxide in the MBK_S.14 and KDK_S.20 samples are consistent with abundant talc minerals.Samples MBK_S.9 and KDK_S.19 of this type group exhibited lower silica concentrations and higher sodium, magnesium, calcium and Iron oxide content.The higher concentration of titanium dioxide (1.5%) differentiates Kongo Type C sample MBK_S.9.
Differences in elemental composition indicate Kongo Type D samples, indicating lower silica content and relatively higher concentrations of sodium (1-5%), calcium (1-5%), and potassium oxide in the range of 44% to 63% (1-5%) due to the presence of feldspar.Furthermore, higher titanium dioxide content (1-3.5%) was observed in this type of group.The high iron oxide content of Kongo D-type samples MBK_S.15, MBK_S.19 and NBC_S.23 is associated with higher magnesium oxide content, which is consistent with the dominance of amphibole.High concentrations of manganese oxide were detected in all Kongo D-type samples.
The main element data indicated a correlation between calcium and iron oxides in Kongo type A and D tanks, which was associated with the enrichment of sodium oxide.Regarding the trace element composition (Supplementary 6, Table S1), most Kongo D-type samples are rich in zirconium with a moderate correlation with strontium.The Rb-Sr plot (Fig. 7) shows the association between strontium and Kongo D-type tanks, and between rubidium and Kongo A-type tanks.Both Kindoki Group and Kongo Type C ceramics are depleted of both elements.(See also Supplementary 6, Figures S16-S19).
XRF data.Scatter plot Rb-Sr, samples selected from Congo Kingdom pots, color-coded by type group.The graph shows the correlation between Kongo D-type tank and strontium and between Kongo A-type tank and rubidium.
A representative sample from Mbanza Kongo was analyzed by ICP-MS to determine trace element and trace element composition, and to study the distribution of REE patterns between type groups.Trace and trace elements are extensively described in Appendix 7, Table S2.The Kongo Type A samples and Kongo Type D samples MBK_S.7, MBK_S.16, and MBK_S.25 are rich in thorium.Kongo A-type cans present relatively high concentrations of zinc and are enriched in rubidium, while Kongo D-type cans exhibit high concentrations of strontium, confirming the XRF results (Supplementary 7, Figures S21–S23).The La/Yb-Sm/Yb plot illustrates the correlation and depicts the high lanthanum content in the Kongo D-tank sample (Figure 8).
ICP-MS data.Scatter plot of La/Yb-Sm/Yb, selected samples from the Congo Kingdom basin, color-coded by type group.Kongo Type C sample MBK_S.14 is not depicted in the figure.
REEs normalized by NASC47 are presented in the form of spider plots (Fig. 9).The results indicated an enrichment of light rare earth elements (LREEs), especially in the samples from Kongo A-type and D-type tanks.Kongo Type C showed higher variability.The positive europium anomaly is characteristic of Kongo D type, and the high cerium anomaly is characteristic of Kongo A type.
In this study, we examined a set of ceramics from three Central African archaeological sites associated with the Kingdom of Congo belonging to different typological groups, namely the Jindoki and Congo groups.The Jinduomu Group represents an earlier period (early kingdom period) and exists only at the Jinduomu archaeological site.The Kongo group—types A, C, and D—exists in three archaeological sites simultaneously.The history of King Kong Group can be traced back to the kingdom period.It represents an era of connecting with Europe and exchanging goods within and outside the Kingdom of Congo, as it has been for centuries.Compositional and rock texture fingerprints were obtained using a multi-analytical approach.This is the first time Central Africa has used such an agreement.
Kindoki Group’s consistent compositional and rock structure fingerprints point to unique Kindoki products.The Kindoki group may be related to the time when Nsondi was an independent province of the Seven Congo dia Nlaza28,29.The presence of talc and vermiculite (a low-temperature product of talc weathering) in the Jinduoji Group suggests the use of local raw materials, as talc is present in the geological matrix of the Jinduoji site, in the Schisto-Calcaire Formation 39,40 . The fabric characteristics of this pot type observed by texture analysis point to non-advanced raw material processing.
Kongo A-type pots showed some intra- and inter-site compositional variation.Mbanza Kongo and Kindoki are high in potassium and calcium oxides, while Ngongo Mbata is high in magnesium.However, some common features distinguish them from other typological groups.They are more consistent in the fabric, marked by the mica paste.Unlike Kongo type C, they show relatively high contents of feldspar, amphibole and iron oxide.The high content of mica and the presence of tremolite amphibole distinguish them from the Kongo D-type basin, where actinolite amphibole is identified.
Kongo Type C also presents changes in the mineralogy and chemical composition and fabric characteristics of the three archaeological sites and between them.This variability is attributed to the exploitation of any available raw material sources near each production/consumption location.However, stylistic resemblance was achieved in addition to local technical tweaks.
Kongo D-type is closely related to the high concentration of titanium oxides, which is attributed to the presence of ilmenite minerals (Supplementary 6, Fig. S20).The high manganese content of the analyzed ilmenite grains associates them with manganese ilmenite (Fig. 10), a unique composition compatible with kimberlite formations48,49.The presence of Cretaceous continental sedimentary rocks—a source of secondary diamond deposits following erosion of pre-Cretaceous kimberlite tubes42—and the reported Kimberlite field of Kimberlite in the Lower Congo43 suggest that the wider Ngongo Mbata area may be the Congo (DRC) Source of raw materials for D-type pottery production.This is further supported by the detection of ilmenite in one Kongo Type A sample and one Kongo Type C sample at the Ngongo Mbata site.
VP-SEM-EDS data.MgO-MnO scatter plot, selected samples from Mbanza Kongo (MBK), Kindoki (KDK) and Ngongo Mbata (NBC) with identified ilmenite grains, indicating manganese-titanium ferromanganese based on Kaminsky and​​Belousova’s research Mine (Mn-ilmenites).
Positive Europium anomalies observed in the REE mode of the Kongo D-type tank (see Figure 9), especially in samples with identified ilmenite grains (eg, MBK_S.4, MBK_S.5, and MBK_S.24) , possibly associated with ultrabasic igneous rocks rich in anorthite and retaining Eu2+.This REE distribution may also explain the high strontium concentration found in the Kongo D-type samples (see Fig. 6) because strontium replaces calcium50 in the Ca mineral lattice.The high lanthanum content (Fig. 8) and the general enrichment of LREEs (Fig. 9) can be attributed to ultrabasic igneous rocks as kimberlite-like geological formations51.
The special compositional characteristics of Kongo D-shaped pots link them to a specific source of natural raw materials, as well as the inter-site compositional similarity of this type, indicating a unique production center for Kongo D-shaped pots.In addition to the specificity of the composition, the tempered particle size distribution of Kongo D type results in very hard ceramic articles and indicates intentional raw material processing and advanced technical knowledge in the production of pottery52.This feature is unique and further supports the interpretation of this type as a product targeting a specific elite group of users35.Regarding this production, Clist et al29 suggest that it may have been the result of an interaction between Portuguese tile makers and Congolese potters, as such know-how had never been encountered during the kingdom and before.
The absence of newly formed mineral phases in samples from all types of groups suggests the application of low temperature firing (< 950 °C), which is also in line with ethnoarchaeological studies conducted in this area53,54.In addition, the absence of hematite and the dark color of some pottery pieces are due to reduced firing or post-firing4,55.Ethnographic studies in the area have shown post-fire processing properties during pottery manufacturing55.Dark colors, mainly found in Kongo D-shaped pots, can be associated with target users as part of their rich decor.Ethnographic data in the wider African context supports this claim, as blackened jars are often considered to have specific symbolic meanings.
The low concentration of calcium in the samples, the absence of carbonates and/or their respective newly formed mineral phases are attributed to the non-calcareous nature of the ceramics57.This question is of particular interest for talc-rich samples (mainly Kindoki Group and Kongo Type C basins) because both carbonate and talc are present in the local carbonate-argillaceous assemblage-Neoproterozoic Schisto-Calcaire Group42,43 Mutually.The intentional sourcing of certain types of raw materials from the same geological formation demonstrates advanced technical knowledge related to the inappropriate behavior of calcareous clays when fired at low temperatures.
In addition to the intra- and inter-field compositional and rock structure variations of Kongo C pottery, the high demand for cookware consumption has allowed us to place the production of Kongo C pottery at the community level.Nonetheless, the quartz content in most Kongo C-type samples suggests a degree of consistency in pottery production in the kingdom.It demonstrates the careful selection of raw materials and advanced technical knowledge related to the competent and suitable function of the Quartz Temper Cooking Pot58.Quartz tempering and calcium-free materials indicate that raw material selection and processing also depend on technical functional requirements.