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Sunday, 7 April 2024

Looking for the origins of garnets from Lower Nubia.

From about the third century BC, garnets became highly valued gemstones to the peoples of the Mediterranean Basin, the Middle East, India, Sri Lanka, Southeast Asia, and China, along with other hard gemstones, such as emerald, aquamarine, and sapphire. Transparent red garnet was used to make engraved rings or seal stones; inlays in diadems; earrings or necklaces or even small sculptures; thin, doubly polished plates in cloisonné jewellery, as well as simple beads, merely drilled to be assembled into necklaces, bracelets, or applied to garments. Studies of garnets dating from the Hellenistic Period to Early Medieval times have identified seven distinctive garnet types (A-G), with unique compositions, some of which have been linked to sources in Europe, India, or Sri Lanka, while the source of others remains unknown.

Garnets were also used as gemstones prior to the Hellenistic Period in several places, although the origin and typology of these is less well understood. Green grossular, a calcic garnet, often intergrown with green vesuvianite was used to make seals, beads, and amulets by the Indus Valley Civilization, and to much lesser extent in ancient Mesopotamia. This material was worked in Harappa, Mohenjo-Daro, and Loal-Mari on the Indus River, and was probably sourced in Balochistan and northern Pakistan. Both grossular and vesuvanite have hardnesses of between 6.5 and 7.0 on the Moh scale (i.e. are slightly softer than quartz) making it possible to work these materials with the tools available to the Indus Valley Civilization.

Red aluminous garnet, however, is harder than quartz, making it much more difficult to work without specialist tools, and is rare in Asia before the advent of the Iron Age. Surprisingly, this material was worked early in Northeast Africa, with red garnet beads known from Predynastic Egypt and the contemporaneous A-group Cultures of Lower Nubia. The use of red garnet continued in Egypt till around the end of the New Kingdom, after which the mineral is seldom found. Thus, the red garnets of Egypt and Nubia are the oldest known examples of the working of this mineral.

In a paper published in the journal Archaeometry on 7 March 2024, Albert Gilg of Engineering Geology at the Technical University of Munich, Joanna Then-Obłuska of the Antiquity of Southeastern Europe Research Centre at the University of Warsaw, and Laure Dussubieux of the Elemental Analysis Facility at the Field Museum, present the results of an analysis of 34 garnet beads from burials in Lower Nubia, dated from the late A-Group to the Post-Meroitic, an age range of about 3200 BC to about 600 AD, as well as two garnets from separate alluvial deposits near the Fourth Cataract of the Nile in the Bayuda Desert of Upper Nubia.

Ancient Nubia is divided into Lower Nubia, which lay between the First and the Second Cataracts of the Nile, and Upper Nubia, to the south of the Second Cataract. Gilg et al. selected beads excavated  from graves in Qustul, Adindan, and Serra East, in the collection of the Museum of the Institute for the Study of Ancient Cultures at the University of Chicago, associated with the Early Nubian A-group Culture, the Middle Nubian C-group and Pan Grave cultures, and the New Kingdom, Napatan, Meroitic, and Post-Meroitic/Nobadian periods.

The A-group Culture (roughly 3700 to 2800 BC) and C-group Culture (roughly 2300 to 1550 BC) are known to have been wealthy societies, due to their location at a junction of trade routes between Egypt and the Mediterranean to the north and the African interior to the south. The Pan Grave people (2200 to1550 BC) lived in small, dispersed groups in the Eastern Desert. All of these peoples traded to differing extents with the Pre-Kerma and Kerma cultures of Upper Nubia. Between about 1570 and about 1069 BC Nubia was controlled by the Egyptian New Kingdon, then between 747 and 656 BC, Egypt was ruled by the Kushite 25th Dynasty, which ruled an area from the confluence of the Blue and White Niles to the Mediterranean. This interval forms part of the Napatan Period in Nubia, which lasted from about 750 BC to about 350 BC, and was another period of wealth in Lower Nubia. This was followed by the Meroitic Period, from about 350 BC to about 350 AD, when Lower Nubia became an intermediary in trade between the Kingdom of Meroë in Upper Nubia and the Hellenic and Roman rulers of Egypt. Between about 350 and 600 AD Lower Nubia was Kingdom of Nobadia, which often had less peaceful relations with both Egypt and the Blemmye peoples who controlled the Eastern Desert and the Red Sea Coast.

Map of Nubia. Gilg et al. (2024).

Gilg et al. analysed garnet beads from tombs 11, 17, 22, 24 of Royal Cemetery L at Qustul, which have been dated to Late A-Group/Naqada III (Naqada III is the final phase of Predynastic Egypt), as well as the late A-Group tombs W19 and V59; garnets from these tombs were commonly accompanied by similarly shaped carnelian beads. Another bead was from the  C-Group Phase III tomb T12B at Adindan, which is of equivalent age to the Egyptian 18th Dynasty (the first dynasty of the New Kingdom). Five more beads come from tombs K74 and K93 at Adindan, which were associated with the Pan Grave Culture; notably, garnet beads are more common in Pan Grave Culture burials than C-Group Culture burials, despite the two being roughly contemporary. Six more beads came from New Kingdom tombs VC45 and R19 at Qustul, three from the Amenhotep III to Amarna Period and three from the post-Amarna Period. A single short barrel bead came from the 25th Dynasty/Napatan tomb W43 at  Qustul. Also from Qustul came an oblate bead from the Meroitic tomb Q465, and a truncated hexagonal bicone bead from the Post-Meroitic tomb Q143.

Beads associated with the A-Group culture are all less than 5 mm in diameter and 2.5 mm wide. They were shaped into short cylinders, barrels, or oblates with a relatively poor polish, and perforated from each end by irregular pecking. Similar beads are known from Predynastic Upper Egypt, which were presumably made in the same way, possibly from the same people. A single bead of similar appearance has also been found at Mehrgarh in Pakistan, which is exotic to that site, but of unknown origin. C-Group and Pan Grave Culture beads are also typically poorly polished and of imperfect shape, though the shape varied slightly, with both rounded and short-barrel beads found. These beads were perforated from each end by drilling, forming either cylindrical or conical holes; the smooth nature of the hole suggests the drill made from a hard stone, such as flint, or possibly copper. Similar perforations have been observed in Middle Kingdom garnet beads from Egypt. Workshops producing carnelian beads are known from A-Group and C-Group sites in Lower Nubia, and while no trace of garnet-working has been found at these sites, the similarity between the carnelian and garnet beads suggests that the garnet beads are also likely to have been manufactured locally.

Microphotographs of garnet beads from lower Nubia. (a) A-group bead with irregular pecked hole (ISAC 13); (b) Pan Grave bead with a smooth drilled hole (ISAC 21); (c) C-group bead with silver beads (ISAC 20);  (d) New Kingdom long barrel-shaped beads with poor polish (ISAC 29-31); (e) Meroitic irregular oblate bead (ISAC33); (f) Post-Meroitic facetted bead (ISAC 34); (g) drill hole (about 1 mm in diameter) with concentric deep grooves from a diamond tipped drill (ISAC 34); (h) tiny short- and long-prismatic colourless inclusions (ISAC 34). Scale bar is 500μm. Gilg et al. (2024). 

The New Kingdom beads showed much improved shaping. The majority of these beads were globular in shape, but also present were unusually long barrel to tubular shapes with a length of up to 7.9 mm and a diameter of 4 mm. These beads all have a low polish, and again are drilled from both ends. The Napatan and Meroitic beads were similar in form to the Pan Grave and C-Group beads.

None of these beads had a high polish, something seen in Egyptian beads from the Great Aten temple at Amarna (18th Dynasty), which were made by polishing with corundum powder as an abrasive, a technique apparently unknown in Upper Nubia. How the Upper Nubian beads were polished is unclear at this time.

The youngest, Post-Merotic bead differs from all others in the study, having a faceted shape (a hexagonal truncated bicone), a well-polished surface, and deep, regularly spaced, concentric grooves in the drill hole, probably indicative of the use of a diamond drill bit. Similar garnet beads are known from Arikamedu in southern India, and sites in southern Sri Lanka. Microscopic examination of this bead revealed the presence of many tiny, short- and long-prismatic, colourless inclusions, something seen in Sri Lankan garnets but not garnets from southern India. Though this is not sufficient evidence to confirm the origin of this bead, Gilg et al. consider it highly likely that this bead comes from South Asia, and probably Sri Lanka.

Chemically, all of the garnets, including the alluvial samples from Upper Nubia were found to be of similar composition, with the exception of the single Post-Merotic bead. These beads have an almandine-rich composition, with a low calcium content (the Post-Merotic bead has a pyrope-rich composition with a low calcium content). Compositionally, these beads do not fit into any of the types used to classify Hellenistic to Early Medieval garnets, with magnesium oxide-calcium oxide ratios intermediate between type A and type B contents, combined with a high manganese and yttrium, low chromium composition not seen in either of these types. This suggests that the beads were made from alluvial garnets sourced from deposits in Upper Nubia, and that garnets from this source were not used in the Hellenistic to Early Medieval periods.

Almandine-rich garnet was the first mineral harder than quartz to be worked in northeast Africa, apparently being sourced at a site in the Bayunda Desert of Upper Nubia at least 670 km south of the most southerly known occurrence of worked garnet beads in Lower Nubia. These Upper Nubian deposits appear to have been the only source of garnets used in manufacturing for at least 3500 years. 

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