Amber provenance was determined using Fourier-Transform Infrared Spectroscopy (FTIR), a well-established technique for distinguishing between amber types based on their diagnostic spectral characteristics. For example, Baltic amber is identified by its characteristic ‘Baltic shoulder’, consisting of prominent absorption peaks between 1160 and 1150 cm⁻¹, preceded by a broad horizontal band spanning 1250-1180 cm⁻¹ (Beck et al., 1964, 1965; Beck, 1982, 1986). In contrast, Sicilian amber exhibits a principal band at 1245 cm⁻¹, accompanied by secondary bands around 1182 cm⁻¹ (Beck and Hartnett, 1993; Angelini and Bellintani, 2005). Iberian Cretaceous ambers are characterized by peaks at 1456, 1376, 1155, and 1030 cm⁻¹, along with a secondary feature at 1226 cm⁻¹ (Peñalver et al., 2007; Murillo-Barroso et al., 2018).

The provenance of the amber bead from Bela Vista was determined by comparing its FTIR spectrum to these reference profiles. Spectral data were collected using a Nicolet iS5 FTIR spectrometer with an iD7 ATR module. Each sample was scanned 64 times across the 4000-525 cm⁻¹ range, at a resolution of 4 cm⁻¹. This procedure ensures high accuracy and reproducibility, facilitating a reliable provenance determination.

In order to contextualize the bead chronologically, the FTIR results were integrated with stratigraphic and typological data (Garrido-Cordero et al., 2024). This included evaluating the bead’s stratigraphic position, associations with other artifacts, and typological traits. These data were cross-referenced with established chronological frameworks for amber consumption on the Iberian Peninsula, enabling assessment of whether the bead corresponds to the Bronze Age, Iron Age, or an earlier period.

The greenstone beads—historically labeled as ‘callaite’—were analyzed using the MACLAS framework, a supervised machine learning (ML) approach for mineral identification based on elemental composition. MACLAS employs a gradient boosting classifier trained on geochemical data to distinguish both major mineral classes (e. g., phosphates, silicates) and specific mineral species (e. g., variscite, muscovite), with confidence scores indicating the reliability of each classification. This non-destructive method enables fast and accurate mineral identification.

For beads identified as phosphate minerals, their provenance was further assessed using the VORTEX (Variscite Origin Recognition Technology X-ray based) framework. VORTEX applies a Random Forest classifier trained on a comprehensive dataset of Iberian variscite sources, enabling probabilistic assignment of beads to specific geological deposits. The model provides accurate provenance predictions with a confidence threshold of >0.7, and has been externally validated, achieving 95 % accuracy in source classification.

Elemental composition data were obtained using an Oxford Instruments XMET-7500 handheld X-ray fluorescence (XRF) spectrometer, equipped with a rhodium X-ray tube, silicon drift detector (SDD), and an automated 5-position filter changer. Quantification was conducted using the SOILS-LE calibration program, which applies the fundamental parameters (FP)⁴ method for precise elemental analysis.

The combined use of MACLAS and VORTEX provides a robust and reproducible approach for characterizing the mineralogical composition and determining the geological provenance of green phosphate beads in archaeological contexts.

The FTIR spectra of bead 533.6.4_6 confirm that the raw material is Baltic amber, as evidenced by the presence of the characteristic ‘Baltic shoulder’. This feature is defined by strong absorption bands at ~1160 and 1150 cm⁻¹, preceded by a horizontal band from 1250 to 1180 cm⁻¹ (Beck et al., 1964, 1965; Beck, 1982, 1986), confirming a Baltic provenance (Fig. 4).

On the Iberian Peninsula, Baltic amber beads are predominantly associated with the Bronze and Iron Ages, based on radiocarbon-dated contexts (Garrido-Cordero et al., 2024). The amber bead from Bela Vista, while undated, has been tentatively linked to Bell Beaker pottery (Leisner, 1965, pp. 85-87; Ferreira, 1966, p. 63). However, the excavators (Mello et al., 1961) reported significant stratigraphic disturbance due to looting, undermining this attribution. Similar issues are present at sites like Larrarte (Beasain, Guipúzcoa) (Mujika and Armendáriz, 1991; Álvarez Fernández et al., 2005), El Bosc I (L’Espunyola, Barcelona) (Serra, 1927; Rovira i Port, 1994, 1996), and Sepulcre de la Pera (Pinós, Lleida) (Castany Llusà and Guerrero Sala, 2010), where amber beads were found near Bell Beaker pottery under ambiguous stratigraphic conditions.

Recent studies indicate that Bell Beaker funerary contexts in inland Iberia frequently include exotic objects, such as amber, marine shells, flint, gold, and variscite. These objects were not necessarily deposited with the same individuals, suggesting complex burial practices and structured spatial associations (Barroso et al., 2015, p. 168). However, Du Gardin (1998, p. 347) emphasizes the limited and highly selective use of amber, primarily in funerary contexts, with only a small fraction of Beaker-associated burials containing it. Alday Ruiz (2018) cautions against assuming a direct link between such materials, noting that the spatial distributions of Bell Beaker pottery, amber, and variscite only partially overlap.

The presence of Baltic amber and Bell Beaker pottery at sites such as Bela Vista may be due to:

In Larrarte, for example, a Baltic amber bead was found alongside Bell Beaker pottery, but radiocarbon dates from the tomb span 4236-1690 cal BCE⁵, with the final burial dated to 2289-1690 cal BCE (Mujika and Edeso, 2011)⁶, suggesting the bead belongs to the Early Bronze Age. El Bosc I, another example, included late Bell Beaker pottery, a glass bead, and amber beads, dated to the Middle Bronze Age (Rovira i Port, 1994, p. 82). The Baltic origin of those amber beads was recently confirmed (Garrido-Cordero et al., 2024).

At Sepulcre de la Pera, despite stratigraphic issues, the presence of Pyrenean-style Bell Beaker pottery and Baltic amber supports a Bronze Age use (~2000-1500 cal BCE) (Castany Llusà and Guerrero Sala, 2010, p. 29).

These cases suggest that the Bela Vista amber bead could date to the Early Bronze Age (2200-1800 BCE), overlapping with the final phases of Bell Beaker use in Portuguese Estremadura (Cardoso, 2014). However, the presence of Iron Age materials in Level C1, such as wheel-thrown pottery and a Hallstatt-type silver bow fibula (Vilaça and Cardoso, 2017), complicates a straightforward association.

The fibula, described by Vilaça (2006), and Vilaça and Cardoso (2017) as a double-spring fibula, lacks the typical breaks for the pin and pin-holder (Fig. 5), raising doubts about its identification.

Further evidence from Quinta do Marcelo (Setúbal), a site with no Bell Beaker pottery, strengthens an Iron Age connection. There, a Baltic amber bead was found in waste pit 2 (level 1), together with a double-spring bronze fibula and high-end artifacts (Soares and Arruda, 2017, pp. 243-244). Radiocarbon dates for this context (1439-209 cal BCE) (Melo and Senna-Martínez, 2001) and associated materials support a Late Bronze to Early Iron Age attribution.

Silver fibulae are rare in pre-Roman Iberia, though not unprecedented. Examples include one from El Acebuchal (Carmona, Seville, 7^th-5^th centuries BCE) and another from a cremation at the northeast wall of Ampurias (Girona, late 6^th century BCE) (Bonsor, 1899, pp. 24-27; Navarro, 1970, p. 56; Ferrer Albelda, 2014, p. 395). Comparable silver fibulae are also known from Punic necropolises, such as Douïmés (Carthage, 8^th-7^th centuries BCE) (Delattre, 1897). If the Bela Vista coil is indeed a fibula, the bead may date to the 7^th-5^th centuries BCE. Alternatively, the coil could have functioned as a bead—an interpretation supported by a silver washer misidentified as a black stone bead by Pina (2019) (Fig. 6). Parallels for such silver bead assemblages come from Phoenician-Punic tombs such as Aïn Dalia Kebira (Tangier), where similar components are recorded (Blaschta et al., 2024, p. 164, fig. 5).

In the Iberian Peninsula, a similar association between Baltic amber objects and Late Bronze/Iron Age bronze wire coil can also be observed, as in the reuse of megalithic structure of Llano de la Sabina 99 (Gorafe, Granada) (Lorrio, 2008, p. 187; Murillo-Barroso et al., 2018).

Compounding the ambiguity are 15 copper-based artifacts⁷, including arc-shaped filaments, which could represent fragments of bronze rings, fibulae, or earrings (Mello et al., 1961; Pina, 2019, p. 61, fig. 181), highlighting the disturbed nature of Level C1 and strengthening the association with an Iron Age deposit.

The co-occurrence of amber and wire-coiled beads is a hallmark of elite Iron Age burials, especially in the Balkans (11^th-6^th centuries BCE) (Ivanova and Kuleff, 2009, pp. 27-32). One notable example is a female burial near Gradets (Bulgaria), which included amber, bronze and silver spiral beads, and fibulae. A striking parallel from Djurslöv (Sweden) features a young woman buried with alternating amber and silver coiled beads suspended between two bronze fibulae (Lundqvist, 2018, pp. 70-73).

These Mediterranean and European analogies suggest that the Bela Vista assemblage represents a high-status Iron Age burial, possibly influenced by Phoenician or Mediterranean trade networks. A stylistic reconstruction (Fig. 7) illustrates how the materials may have been worn—amber beads alternating with silver spirals, a cloak fastened with fibulae, and bronze earrings.

Current research indicates that the large-scale circulation of Baltic amber into Iberia did not begin until after 1200 BCE, in contrast to its earlier presence in Central Europe, the Aegean, and the British Isles (Vandkilde et al., 2024). The unique case of a Baltic amber bead from Cova del Frare (Matadepera, Barcelona) dated to the 4^th millennium BCE (Murillo-Barroso et al., 2023) is likely the result of post-depositional movement or contamination, given the implausibility of such an early date (Garrido-Cordero et al., 2024). The site also yielded an Iron Age sword and fusiform glass bead, reinforcing a Late Bronze or Iron Age context (Giró i Romeu and Masachs, 1968; Rafel i Fontanals, 1978).

Therefore, while a tentative association with Bell Beaker contexts cannot be entirely excluded, the cumulative archaeological, stratigraphic, and compositional evidence, together with comparative parallels, strongly supports an Iron Age attribution for the Bela Vista amber bead.

Analysis via the MACLAS (Sánchez-Gómez et al., 2024) classified three beads as variscite (Group VII – Phosphates, Arsenates, Vanadates of Dana’s New Mineralogy; Gaines et al., 1997), with a probability score >97 %. One bead was classified as muscovite, a phyllosilicate from Group VIII (Silicates) (Tab. 3).

The VORTEX model (Sánchez-Gómez et al., 2025, 2026) suggests that beads 533.6.4_1 and 533.6.4_5 likely originate from the Aliste region (Zamora, Spain), with ~86 % confidence, and bead 533.6.4_2 with ~70 %. This supports a Palazuelo de las Cuevas source (Villalobos García and Odriozola, 2016).

While early classifications (Mello et al., 1961; Leisner, 1965) were mostly correct, one bead previously labeled variscite was identified as muscovite. Such mixed assemblages of phosphate, mica, and silicate beads are common. The dominance of variscite suggests long-distance exchange, underscoring Bela Vista’s significance.

The Aliste origin aligns these beads with the Bell Beaker phase (2600-1800 BCE) (Odriozola et al., 2016), supported by variscite’s declining availability in the 2^nd millennium BCE.

Although the available evidence strongly suggests that the Baltic amber bead from Bela Vista is best attributed to the Iron Age, and that the greenstone beads are more likely associated with a late 3^rd millennium BCE (Copper Age) context, the possibility of an Early Bronze Age (ca. 2200-1800 BCE) attribution for the amber bead cannot be entirely ruled out.

Amber and variscite have been found together in numerous Iberian funerary contexts, including Campo de Hockey tomb E3-C15 (Cádiz; Vijande Vila et al., 2015), Chousa Nova (Pontevedra; Domínguez Bella and Bóveda, 2011), Dolmen de Alberite (Cádiz; Domínguez Bella, 1996; Domínguez Bella et al., 2001), Anta da Capela (Portalegre; Odriozola et al., 2019), Anta Grande do Zambujeiro (Évora; Odriozola et al., 2012, 2019), Anta Grande da Comenda da Igreja (Évora; Leisner, 1965), Anta dos Penedos de São Miguel (Portalegre; Claustre et al., 2005), Alcalar tombs 3 and 4 (Faro; Sousa et al., 2024), São Paulo 2 (Setúbal; Barros and Espíritu Santo, 1997), Las Arnillas (Burgos; Villalobos García, 2016), La Velilla (Palencia; Villalobos García, 2016), Errekatxuetako Atxa (Bizkaia; López Quintana, 2015), Trikuaitzi I (Guipúzcoa; Mujika and Armendáriz, 1991), Cova de la Pastora (Alicante; García-Puchol et al., 2012), Cal Rajolí (Lleida; Serra, 1927), tholos de la Pastora (Seville; Almagro, 1962; Murillo-Barroso et al., 2018), Perdigões tomb 1 and tomb 2 (Reguengos de Monsaraz; Odriozola et al., 2010; Valera, 2017), and Valle de las Higueras 1 and 3 (Toledo; Barroso et al., 2021).

While these associations confirm that amber and variscite could form part of the same burial assemblages, analytical studies consistently indicate that the amber found at these sites is not of Baltic origin. This significantly reduces the likelihood that variscite was ever associated with Baltic amber in prehistoric Iberian contexts, making such a combination—like that proposed for Bela Vista—highly improbable.

The Baltic origin of the Bela Vista bead therefore aligns more convincingly with an Iron Age chronology. The absence of variscite in Iberian sites with confirmed Baltic amber further reinforces this interpretation and diminishes the plausibility of an Early Bronze Age context for the Bela Vista bead.

Moreover, the scarcity of Baltic amber in pre-Bronze Age Iberian contexts remains a major challenge to such an attribution. As previously discussed, the large-scale introduction of Baltic amber into the Iberian Peninsula only began after ca. 1200 BCE, during the Late Bronze Age (Vandkilde et al., 2024). The exceptional case of a Baltic amber bead from Cova del Frare, dated to the 4^th millennium BCE (Murillo-Barroso et al., 2023), remains an anomaly and is likely the result of post-depositional disturbance or contamination. The same site also yielded Iron Age materials, including a sword and a fusiform glass bead, further supporting a later chronological framework (Giró i Romeu and Masachs, 1968; Rafel i Fontanals, 1978; Murillo-Barroso et al., 2023).

That said, an Early Bronze Age attribution for the Bela Vista bead cannot be categorically ruled out. If the bead was indeed deposited during this period, it would represent a rare—though not unprecedented—instance of Baltic amber reaching western Iberia via long-distance exchange networks linking the Baltic region to Central Europe and, indirectly, to the Iberian Peninsula. This trend can be observed, for instance, in the prestigious burials at Horta do Pinheiro 5 (Torrão do Alentejo), which contain ivory and silver (Monge et al., 2021).

The discovery of a complete amber necklace at Cabecinho da Capitôa (Sousa et al., 2022), located on the northern platform of the Serra de Sintra very close to Bela Vista, is also noteworthy. This find has been radiocarbon dated to the 8^th and 6^th centuries BCE (Sousa et al., 2022). As with other deposits—such as the Iron Age hoard from Palacio III (Almadén de la Plata, Seville; Murillo-Barroso and Martinón-Torres, 2012)—this assemblage does not appear to have served a funerary purpose.

Based on the current archaeological, stratigraphic, and compositional evidence, we propose that the variscite beads from Bela Vista are most plausibly associated with a Copper Age burial, in keeping with broader Iberian patterns of variscite use and circulation during the 3^rd millennium BCE. In contrast, the Baltic amber bead and associated silver wire coil are more credibly linked to an Iron Age burial, most likely dating to the 7^th-5^th centuries BCE. This interpretation is supported by regional patterns of Baltic amber consumption during the Iron Age, the typological features of the associated artifacts, and the complex stratigraphy of the Bela Vista tholos.

While a tentative Early Bronze Age attribution for the amber bead remains theoretically conceivable—especially given that the Beaker horizon extended into the early 2^nd millennium BCE and that Baltic amber exchange had already begun in northwestern Europe—we consider this scenario less likely. The presence of Iron Age materials in the same stratigraphic layer, the extreme rarity of pre-Bronze Age Baltic amber in Iberia, and the contextual and typological parallels all favor an Iron Age attribution.

Our examination of personal adornment materials has enabled the reintegration into scholarly discourse of the amber bead from the Bela Vista tholos, which had remained unaccounted for over six decades. Through FTIR analysis, we have confirmed its Baltic origin. This, coupled with its association with a silver artifact, provides strong support for an Iron Age chronology (7^th-5^th centuries BCE).

The Baltic amber bead from Bela Vista must be understood within two key contextual frameworks: the near-total absence of Baltic amber in pre-Bronze Age Iberia, and its association with silver, a material rarely found in prehistoric funerary contexts in Portugal. While amber is present in Copper Age and Bell Beaker contexts, it is exclusively of Sicilian origin (Murillo-Barroso et al., 2018; Odriozola et al., 2019). Notably, no association exists between Baltic amber and either Bell Beaker vessels or variscite beads in Iberian archaeological contexts. In all documented cases where variscite co-occurs with amber, the latter is Sicilian—never Baltic.

The analytical results presented here, particularly the FTIR identification of Baltic amber and the associated silver coil, further support an Iron Age attribution. This aligns with the emergence of Baltic amber in Iberian contexts ca. 1200 BCE (Vandkilde et al., 2024) and with parallels from Iron Age votive deposits, such as those documented at Palacio III (Murillo-Barroso and Martinón-Torres, 2012), Llano de la Sabina 99 (Murillo-Barroso et al., 2018), Cova del Llidoner (Alicante) and Correio-Mor cave (Lisboa; Garrido-Cordero et al., 2024), where later materials were introduced into earlier megalithic contexts.

We propose that the Bela Vista megalithic tomb was reused during the Iron Age for a high-status funerary deposit, which included a Baltic amber bead, a silver wire-coil, and other bronze objects—likely personal adornments. This secondary use is consistent with a broader pattern of monument reuse in Iberia, where prehistoric tombs were reappropriated for elite burials or ritual depositions in later periods (Lorrio, 2008).

At the same time, the presence of Bell Beaker pottery, Palmela points, and V-perforated buttons, in the primary assemblage confirms the site’s main use during the second half of the 3^rd millennium BCE. An earlier Copper Age phase may also be inferred from the presence of copos canelados, which were identified by Pina (2019) but largely overlooked in earlier publications. These objects suggest a funerary phase, potentially linked to long-distance exchange networks that brought exotic materials such as variscite into the region. However, the limited contextual information in excavation records and museum catalogues hinders a full reconstruction of the original burial sequence.

One of the most significant outcomes of this research is the reidentification of a set of silver disc-shaped beads, previously interpreted as part of a fibula coil. Their morphology, contextual association, and typological features strongly suggest their use as independent ornamental elements. This finding represents a novel contribution to the archaeological record of Portugal, as such items had not been previously documented in Iron Age contexts within the region. Their presence reinforces the interpretation of the Bela Vista tholos as a site of high-status reuse during the Orientalizing period.

Ultimately, this study highlights the value of applying modern analytical techniques to legacy collections. The rediscovery and reclassification of the amber bead—previously thought lost and misidentified—demonstrate the potential of reexamining museum holdings to yield new archaeological insights. The integration of archaeometry with contextual and typological data has clarified the multi-period use of the Bela Vista monument and refined our understanding of long-distance exchange and symbolic practices in prehistoric Iberia.