Metal ornaments from the burial mound necropolis Chornyanka of the Bilozerka culture (11th–10th centuries BC)

. The flat cemetery near the village of Chornyanka, Kakhovka district, Kherson region, is one of the largest row grave fields of the Late Bronze Age archaeological culture of Bilozerka in the northern Black Sea region. The cultural and chronological location of the Chornyanka burial ground was determined on the basis of an analysis of the main features of the funerary constructions, ceremonies and equipment. The established date of its functioning is the 11th‒10th century BC. 24 graves were identified and investigated. Most contained grave goods: pottery, bone and bronze tools, jewellery of bronze, bone, agate, mother-of-pearl, chitin and glass. This paper presents the results of metallographic and X-ray spectral analysis of bronze jewellery from Chornyanka cemetery: pins, temple rings and earrings. It presents and describes the characteristic microstructures of the metal finds. In addition, the process of production of various metal objects was investigated. Several chemical and metallurgical groups stand out in the spectral analyses of metals from Chornianka:

Temporal rings, regardless of their size, were placed on the skull or under the skull close to the auditory canal. There is no doubt that rings of small diameter are earrings. They have either one pointed end or both are blunt. Table 1 shows the parameters of these ornaments: diameter, wire thickness and others. In general, they can be divided into three groups. The first group consists of five large rings with a diameter of 40-44 mm, made of wire 2-4 mm thick, round or rectangular in cross-section. Both ends of the wire are pointed (2 rings), or only one (2 rings), or both are blunt (1 ring).   The second consists of three rings of medium size -30-38 mm in diametermade from wire of the same thickness as the large rings (3-4 mm). In one case the wire is flattened in the center, the others have a round cross section. A pointed end of the wire in 2 rings; one has both blunted.
Small rings, probably earrings, with a diameter of 16 to 27 mm (7 specimens) are part of this group. The thickness of the wire varies from 1.5 to 4 mm, one of them is flattened in the middle. Four ends are blunt. Three ends are pointed.
Temple rings and earrings are mainly women's and children's jewelry. Men's clothing also shows similar decoration. However, it is much rarer. Temple rings and earrings were found in only one burial, No. 2 at Chornyanka 1 . In another ground necropolis of the Bilozerka culture, Shyroke, the same ornaments are more frequently found in the accompanying inventory of male burials. Temple rings and an earring were found in burials 30, 40 and 107 (Kravchenko, 2019, pp. 48, 57, 118). It should be noted that the skeleton of a man 2 from burial 107 was lying on his left side and had, in addition to two temple rings, a pin with a looped head (Kravchenko, 2019, p. 118, fig. 1.118, 2).

Results and discussion.
Spectro-analytical (17) and technological (12) studies of the products from Chornyanka have been carried out. Technological details of production were revealed in the process of visual surface examination of objects with the help of binocular microscope MBS-200. The metallographic analysis was carried out with a MIM-7 microscope, and a PMT-3M micro-hardness tester was used to measure microhardness. The surfaces of the products cleaned of oxides were subjected to metallographic and X-ray fluorescence analyses.
https: //www.hst-journal.com Історія науки і техніки, 2023, том 13, випуск 1 History of science andtechnology, 2023, vol. 13, issue 1 X-ray fluorescence analysis 3 . The determination of cobalt (Co) and bismuth (Bi) by this spectrometer makes it impossible to include these two elements in the analysis. As shown in Table 2, small concentrations of cobalt and bismuth in the metal are sometimes indicated in the analyses. The X-ray fluorescence results in the table are grouped by selected compositions.
Several chemical and metallurgical groups have been identified in the metal samples from Chornyanka: Сu-Sn; Сu-Sn-As; Сu-As(Sn) and possibly remelting.
The second group, Сu-Sn-As, can be considered as a double tin-arsenic alloy. It includes five analyseslab. No. 123,125,126,129 and 997.
The content of tin in the metal composition is lower: from 1.066 to 2.781%, and the concentration of arsenic slightly increases in comparison with the previous group (from 0.759 to 1.516%).
Three analyses are included in the group of arsenic bronzes Сu-As(Sn): lab. No 128, 1003 and 1002. As in the previous group, the analyses of the third group contain a rather significant percentage of arsenic (As -0.848-1.463%).
The appearance of such low percentages of tin in the analyses of this group can be explained either by its transition into metal from copper ore or by the use of remelted products.
A similar metal with a reduced tin content (from 0.1 to 0.8%), known from the Caucasus in the Late Bronze Age, is called "conditionally tin bronze" by S. M. Korenevskyi (Korenevskyi, 1981, p. 148).
It is probable that the metal of the two temporal rings (lab. No 121 and 130) also belongs to the bronzes mentioned above. Alternatively, it may be a re-melted alloy, given the low content of both tin and arsenic.
It is noteworthy that in all analyses arsenic is present in tenths of a percent, as well as the stable presence of antimony, mostly in tenths of a percent, with concentrations reaching whole percent in two cases (lab. No 130 and 392). These minerals were probably part of the original ores. According to S. M. Korenevskyi, this feature is typical for the metallurgy of the Greater Caucasus (Korenevskyi, 1981, p. 153).
The study of the Shyroke metal suggested that it was smelted from Caucasian ores (Hoshko, 2019b, pp. 165, 172). Based on the correlation graphs of metal element pairs from the Chornyanka and Shyroke cemeteries, we can claim a great similarity (Fig. 3). It is particularly noticeable in the graphs of Sb-Ag and Sb-Pb. So there is reason to believe that the masters of the Bilozerka culture imported metal from the Greater Caucasus. However, we can only talk about the population living in the lower reaches of the Dnipro. E. A. Kravchenko also does not exclude a possible connection with the Caucasus (Kravchenko, 2019, p. 160). She draws attention to the similarity of the burial rites of the Bilozerka and Koban cultures and to the conclusions of anthropologists on the morphological similarity with some series of skulls from the Caucasusfrom the Samtavro cemetery (second variant) (Zinevych & Kruts, 1968, p. 89 Technological study. A total of 12 items were subjected to metallographic examination: 11 temple rings and one pin (Fig. 4, Fig. 5).  There is not enough information on the effect of forging at different temperatures on copper with arsenic content up to 1%, despite an interesting and necessary work by Ravich and Ryndina (Ravich & Ryndina, 1999, pp. 77-98). Arsenic bronze castings have a dendritic structure. It was found that dendritic liquation in copper-arsenic alloys is more stable than in tin bronzes. It is preserved after high degrees of compression and after annealing. Therefore, it can only be stated that the temperature regime of the forging billets was in the range of the onset of recrystallisation (350°C) and in the range of the final recrystallisation (400-700°C). Microstructures: 1lab. No. 267;2lab. No. 268;3lab. No. 269;4lab. No. 270;5lab. No. 271;6lab. No. 272.

Figure 5.
The technological scheme for the production of wire products was as follows. The wire was made from a cast billet forged on a special anvil with a chute. It is impossible to determine whether the forging was carried out in cold metal with annealing or in a hot state. However, given the residual more or less deformed microstructure of the castings, the billets were mainly heated to an incandescent temperature of 500C. The workpiece was then cut into the required lengths, sometimes with one or both ends sharpened. Sometimes both ends were left blunt. Finally, the rings themselves were formed. Sometimes the bent ring was additionally flattened on the sides (lab. No. 261/120,263/121,264/123,266/125).
I feel it is necessary to remind you that the metallographic analyses were carried out on whole objects and the location of the grinding was in the central part of the ring. Therefore, the information about the forging temperature and the degree of crimping applies only to the central part of the rings. Accordingly, the deformation was undoubtedly more intense at the pointed ends.
Two pieces of jewellery are interesting from a technological point of view: an earring from grave 13 (lab. No. 262/121) with round wire cross-section and blunt converging ends and a large temporal ring from grave 19 (lab. No. 265/124) made of round wire with converging blunt ends ( Fig. 1.5, Fig. 1.8).
Microstructural analysis revealed the presence of a blacksmith's seam on both. There is a branching weld on the earring and a barely noticeable weld on the temporal ring ( Fig. 4.2, Fig. 4.5). The microstructure of the earring is a deformation texture with small recrystallised grains with twins on a background of smooth elongated dendrites by forging. The grain size is 0.025 mm. Microhardness 98.6 kg/mm 2 . Despite the fact that a fairly high degree of deformation has been applied, welding has been unsuccessful, although the seam is not visible from the outside.
However, the welding of the temporal ring was successfulthe seam is almost invisible. The strain was higher because the cast structure is more deformed and the percentage of recrystallised structure is higher than in previous analyses. The grain size with twins is 0.035 mm. Microhardness 134.6 kg/mm 2 .
All that remains of the pin is a fragment of the rod with the remains of the head (lab. No. 272/392). The pin was made by free forging from a rectangular billet (the outer seam formed during forging is visible along its entire length) forged to a circular cross section (Fig. 2.1). The head was made from the riveted end of a rod rolled into a loop. Forging was carried out at low temperatures with annealing. The microstructure is residual dendritic against a background of small recrystallised grains with twins ( Fig. 5.6).
Comparing the technologies of jewellery production at Chornianka and Shyroke cemeteries, we see that in both cases metalworking schemes were used to make temple rings and earrings, which involved casting blanks and then forming them on a fluted anvil with a shaped lining. This explains the uniform thickness and round cross-section of the wire on many products.
Forging at both sites took place mainly at low temperatures of 400-500°C, sometimes rising to 600-700°C at Shyroke. It is possible that the blacksmiths were aware of the high volatility of arsenic vapours, which is why they preferred to heat the metal to low temperatures.
Blacksmith welding can be traced in both collections. There are two cases in Chornianka and one in Shyroke. Most of the temporal pendants from Shyroke are noticeably flattened on both sides. There are only four in Chornianka. Two pins with looped heads from both sites were made by free forging. The rods still have surface seams on them, which were formed when the billets were forged from square sections.
There is no point in comparing the results of technological analysis from the settlement of the Bilozerka culture Dykyi Sad. That collection is more diverse, and the jewellery is represented by a different categorybracelets and hairpins (Horbenko & Hoshko, fig. 1). This explains the variety of technological schemes of metalworking. In general, it is associated with the forging of cast billets at temperatures not exceeding 600ºC.

Conclusions.
The nearest to Chornianka in terms of location is the Shyroke necropolis. Therefore, it is best to compare the technology of making metal jewellery from these two sights. There are both similarities and differences between the two collections: 1) the same schemes of metalworking of wire decorations were used; 2) forging at both sights took place mainly at low temperatures of 400-500°C; 3) the degree of crimping of the Chornianka metal was low, mostly 20-40%. At the same time, in the Shyroke collection, craftsmen more often chose a higher degree of crimping of the workpieces -60-80%, less often -20-40%, and sometimes 100%; 4) in both collections, forging welding can be traced. The previously expressed opinion about the possible Caucasian origin of the metal in the Shyroke necropolis is now confirmed by the analysis of metal from Chornianka. Funding.