Shine on you crazy diamond : Symbolism and social use of fluorite ornaments in Iberia’s late prehistory

: Fluorite ornaments have been recorded in different sites of Europe since Upper Paleolithic. Due to its visual appearance and physical properties, some translucent or transparent mineralogies like fluorite were searched for or casually acquired by late prehistory’s human communities. After intensive research on archaeological contexts from the Iberian Peninsula with personal ornaments from 4 th to 2 nd millennia BCE, we have recently identified and characterized for the first time an important number of fluorite ornaments, confronting a previous background where little attention was paid. Our work has been carried out in different archaeological collections and museums from the whole Iberian Peninsula by non-destructive techniques (Raman spectroscopy, portable X-ray fluorescence (p-XRF) and X-ray Diffraction (XRD), that revealed the nature of fluorite ornaments and points to its consideration as scarce and highly symbolic items during late prehistory. A total of 36 fluorite beads from 23 sites are here recorded and studied, many of them unpublished or wrong catalogued as other mineralogies. These adornments could have important roles in trade and use among the communities of Iberia from the 4th millennium BCE onwards, because of their scarcity and its recurrent association with important funerary complex and exotic materials. Fluorite ornaments could have been significant and special symbols in the development of new and exclusive raw materials in the context of increasing social complexity and inequality.

In the Iberian Peninsula, apart from the long-known social value of amber (for a review see Odriozola et al. 2019), transparent or translucent beads are rare, and when recorded they were generally classified as quartz or rock crystal with no further analysis than that of the naked eye.However, besides quartz varieties, there are many more transparent minerals that are not usually considered, for example fluorite, calcite, and many sheet silicates that when thinned to a certain level are capable of transmitting light (Baysal 2017: 6-7).The social value of translucent ornaments made of those minerals would partially stem from its visual and physical properties and its scarcity in the archaeological record (Garrido-Cordero et al. 2020a;2020b).
This paper is focused in the role of fluorite adornments as highly scarce and symbolic items, used among the communities of Iberia's late prehistory, a subject on which little research has been previously carried out.The starting point for this study is a remarkable set of unpublished translucent beads that we have characterized and gathered for the first time.The chemical and contextual analysis of these beads inventoried throws new light on the use and social significance of translucent personal adornments during the increase of social complexity from Late Neolithic to Early Bronze Age.

Fluorite ornaments in late prehistory: The broader European context
In Europe, the small-scale exploitation and consumption of fluorite has been documented in Belgium at Upper Paleolithic sites, mostly during the Magdalenian period (Goemaere et al. 2013;Jungels & Goemaere 2007).In some cases, a large quantity was used, and the mineral was worked in situ (440 g of fluorite at the site of Chaleux) and distributed locally and regionally for the manufacture of adornments (Goemaere et al. 2013).No prehistoric fluorite mines have been identified in Europe.In fact, ethnographic data suggest that outcrops of this type of raw material could have been exploited just occasionally and opportunistically by small groups without any complex logistical organization (Brandl & Trnka 2014: 124).
The frequency of its consumption for objects of personal adornment seems to increase during the Neolithic, but is still small compared with other raw materials.In the late 5 th and early 4 th millennia BCE, some Belgian sites have yielded both manufactured fluorite fragments and others in the process of being made into beads and pendants (Delye et al. 2011;Vermeersch et al. 1990).At Thieusies, several worked fluorite fragments in different colours and four finished beads came to a total weight of 158.4 g (Vermeersch et al. 1990: 51-52).
From the Late Neolithic to the Copper Age (5 th -3 rd millennia BCE) the number of sites where this raw material was used to make adornments increases considerably.Fluorite beads have been found at Neolithic sites in the north of France (Hauzeur & Cauwe 2012: 39), in the Paris Basin (Polloni 2008) and in the south-west, especially between Perpignan and Narbonne (Roscian et al. 1992: 233-234).Their distribution coincides with the main outcrops of fluorite in the Central Massif and the Pyrenees, and supports the idea of local exploitations near the outcrops and distribution on a regional scale.In Predinastic Egypt (4 th millennium BCE), fluorite ornaments are also reported (Nai 2014: 77).
Fluorite continued to be used occasionally for personal adornments in the 2 nd millennium BCE.Fluorite beads are referred at Bronze Age levels in Mol, Belgium (Warmenbol 2001) or Midea, Greece (Demakopoulou et al. 1996).
Unlike other parts of Europe, no personal adornment made from fluorite is known in the Iberian Peninsula before the 4 th millennium BCE, although many sites with fluorite have not been dated by radiocarbon or the finds are not directly associated with a dated level.

Materials and methods
A total of 23 sites in the Iberian Peninsula with a total number of 36 items made of fluorite are reported in this work (Figure 1, Table 1).Archaeological background on the sites studied here can be found at Supplementary Material 1. From this total, 28 fluorite beads from 20 sites were directly analyzed for this paper (Figure 2) by Raman spectroscopy and portable XRF.Also, X-ray diffraction (XRD) has been possible to perform when the museums granted the transport of materials to the laboratory.Raman spectroscopy was performed using a portable BWTEK iRaman Plus device.The laser diode operated with a wavelength of 785 nm produces a power of up to 420 mW in the laser port.Filters were not used to reduce the power of the laser.The selected range of the measurement spectrum was between 150 and 3300 cm -1 with a high efficiency quantum CCD detector.The selected measurement accuracy was 4 cm -1 .The measurement conditions, as regards the laser power and integration time have varied from one object to another in order to obtain the best possible Raman signal.
Chemical composition was measured by an Oxford Instrument XMET-7500 p-XRF equipped with a Rh tube, a silicon drift detector (SDD), and an automatic 5-position filter changer.Quantification was obtained using the SOILS-LE program based on fundamental parameter (FP) method.This method is the most appropriate when no standardized method is available or when a large number of elements have to be analyzed (Beckhoff et al. 2006: 403).XRD analysis was performed using a Panalytical X'Pert Pro θ/θ diffractometer equipped with Cu Kα source (1.5406 Å) operating at 45 kV and 40 mA.A PixCel detector was used and the data were collected on transmission mode with a 2D detector.Patterns were obtained using a step width of 0.053º 2θ between 5º and 70º 2θ and a counting time of 155 s per step at ambient temperatures.An incident beam PreFIX module with X-ray mirror for Cu radiation was used to allow non-destructive analysis.
Beside these features in the diagnostic region, a set of bands appear in the frequency-shift region between 1000 and 2500 cm -1 that are the result of the 785 nm laser induced fluorescence and photoluminescence (PL) (Figure 4).Fluorite PL pattern is most likely due to the presence of REE 3+ ions, mainly Nd, at C 4v sites (Freeth & Jones 1982;Payne et al. 1991).PL bands have been formerly proposed as mineral characteristic (Chen & Stimets 2014), therefore the match between fluorite reference PL spectra and the here recorded would support the identification of all the analyzed specimens as fluorite.However, no exhaustive database exists for mineral identification by means of the PL spectra and their usability is therefore limited and still under research.Recent studies (Zhuk 2017) have shown that in some cases calcite shows PL spectra very similar to that of fluorite leading to a misclassification of the specimen, and therefore preventing the immediate classification of these beads as fluorite.This is true because Ca substitutions by REE elements in calcite crystal lattice result in a similar laser induced photoluminescence to that of fluorite crystals (Gaft et al. 2001).Except for Los Millares specimens that lack the 1137 cm -1 band and show differences in position and intensity of the bands in this region, that might be associated with the accommodation of REE 3+ in substitution for Ca (Chen & Stimets 2014;Cherniak et al. 2001;Lenz et al. 2015;Sverdrup 1968;Tu and Sievers 2002), the spectra of this set of beads (Figure 4) accounts for the typical fluorite PL spectrum (Andò & Garzanti 2014).
Therefore, based on 1) the presence of the T 2g Raman band, 2) the coincidence of the PL of the specimens with that of fluorite, and 3) the chemical composition of the beads; fluorite is proposed as the main mineral phase for these 11 beads.Even though 15 of the analyzed beads (LB-0011, LB-0012, OP-21815B, OP-21815A,    Apart from the aforementioned fluorite beads, ornaments from La Velilla, Vila Nova do São Pedro (ARQ-VNSP-964.064),Cabeço da Ministra (25992-1 and 25992-2), as well as translucent green minerals from Cueva del Vaquero, and La Emisora had a chemical composition and optical properties compatible with that of fluorite (Table 1).

Conclusions. Fluorite consumption in Iberia's late prehistory: Perspectives on its social use and symbolism
The use of fluorite can be circumscribed to the period from the mid-4 th to the mid-3 rd millennia BCE, while a few isolated cases attest an interesting symbolic continuity in the 2 nd millennium in south-east Iberia, in Tomb 111 at Fuente Álamo.So far, only the two fluorite beads from have been documented in that chronology (Pozo et al. 2002;Schubart et al. 2006).
In the Iberian Peninsula, as in France and Belgium, fluorite was used little, either because of the difficulty in finding large fluorite crystals or because of its consideration amongst other transparent and translucent raw materials.Ornaments made with this mineral are present in various types of contexts during the 4 th -3 rd millennia BCE, both funerary and non-funerary.Orthostatic megaliths (16 sites) and natural caves (9 contexts) represent most of the sites where they have been found, as well as in artificial caves (4 sites) and tholoi (3 sites).Two habitational contexts, the Chalcolithic sites of Leceia and Vila Nova de São Pedro, also evidence the consumption of fluorite ornaments (Table 1, Supplementary Material 1).It has only been found at two non-mortuary sites; in the third millennium fortified settlements of Leceia and Vila Nova de São Pedro, which are relatively near to each other by the Tagus estuary.At practically all the sites, the fluorite appears in the form of finished adornments and at present no remains of production or objects in the process of being fabricated are known.The only elements of fluorite in mineral form that are known are both from the Province of Seville: the large piece in the tholos of Cueva del Vaquero (Alcalá de Guadaíra), and in La Emisora sector in Valencina de la Concepción.
The distribution area of the fluorite mineral is mainly situated on the Atlantic seaboard (Figure 1), where sites possess local or regional access to outcrops, or are distant from sources but positioned on strategic nodes of communication.Its distribution therefore appears to be marked by the Douro and Tagus river basins, with their tributaries, and to a lesser extent by the Guadalquivir estuary and the Guadiana basin (Figure 1).An important concentration is in Évora, particularly at Anta Grande da Comenda da Igreja and Anta Grande do Zambujeiro.Although at many archaeological sites the fluorite may have been obtain in the proximity, the fluorite beads from the area of the Tagus estuary have been interpreted as exotic elements arriving through exchange networks, as the best known fluorite outcrops are several hundreds of kilometers away (Cardoso et al. 2012).
The situation around the Tagus estuary, particularly on the Lisbon and Setubal peninsulas, throughout the 3 rd millennium BCE but especially in the first half, seems to support the idea of groups or centers that received rare raw materials (amber, ivory, variscite and fluorite) and "exclusive" or prestigious objects (e.g., votive elements in limestone and lagomorphic pendants).They may have been the final destination of the route that the finds of fluorite at sites near the Atlantic coast seem to draw.A similar situation can be observed around the Guadalquivir estuary, where specially Valencina de la Concepción-Castilleja de Guzmán site (Seville) but also the megalithic necropolis of El Gandul have yielded a large number of exotic objects, burials and unusual raw materials (see García 2013 for a review on Valencina).However, the proximity of outcrops of fluorite at Morón and El Castillo de las Guardas (Calderón 1910: 409) may support a local provenance for that mineral.This may also be the case of fluorite beads in the megalithic monuments in the western Sierra Morena, in Huelva.
The circulation of large heavy pieces is noteworthy and mostly coincides with the most spectacular items that have been found precisely in prestigious mortuary contexts: the beads from São Paulo 2 (26.3 g), Anta Grande do Zambujeiro (26.5 g), Casa da Moura (22.6 g), and bead 2011.54.278 from Anta Grande da Comenda da Igreja (19.8 g) represent 47.3% of the total analyzed in Portugal (171.8 g).The total weight of the 23 fluorite objects from the Iberian Peninsula that have been weighted is 296.6 g.Spanish fluorite objects amount to 124.8 g, of which 90.1 g corresponds to the fragment of mineral at Cueva del Vaquero and 21.2 g to the fluorite bead in Dolmen 6 at Los Gabrieles.
Fluorite's property of light transmission, its transparency or translucence and the fact that it can be tainted a wide palette of colours that are unusual in nature, like pink, violet or blue, most probably lent them social and symbolic significance and invested them with special meanings and connotations.Indeed, it seems that the pink and violet shades, the more unusual ones, appear in the megaliths where individuals of higher rank were inhumed, for example, Anta Grande da Comenda da Igreja, São Paulo 2, Anta Grande do Zambujeiro and Los Millares 12.
Besides its organoleptic properties, it seems therefore reasonable to suggest that fluorite beads would have had an "added value" based on their exoticism and rarity, as characterization allows to compare its rare proportion of use as ornamental raw material.The idea of this special consideration and rareness of fluorite ornaments is strengthened by its proportion compared with other raw materials used for objects of personal adornment: exotica as amber counts to date with 647 items (Odriozola et al. 2019), against the 36 fluorite ornaments reported here.As personal belongings, beads may have been items whose use and possession differentiated certain individuals within their communities, materializing social differences by means of their asymmetric display among the living and the dead.In addition to the former, the association of fluorite beads to other non-local raw material items of great value strongly suggests the high-ranking status of the people wearing such items.For example, Tombs 12 and 63 at Los Millares are considered "prestigious" (Chapman 2008), as the grave goods included pottery with symbolic decoration, singular ivory objects and amber beads (5 and 1 respectively) (Chapman 2008;Leisner & Leisner 1943: 25-26;Odriozola et al. 2019).
The find of large decorated fluorite beads in Anta Grande da Comenda da Igreja and the artificial cave of São Paulo 2 (Figure 2) indicates not only a formal similarity between the two items (practically perfect spherical shapes) and a possible association with the 4 th -3 rd millennia BCE transition, but also their relationship to other prestige items, such as amber beads and lagomorphic pendants (Barros & Espírito-Santo 1997;Leisner & Leisner 1965: 121-122), in these outstanding monuments and their rich grave goods assemblages.Although smaller in size, the fluorite bead from Gruta da Marmota MMT-26 is also decorated with incised vertical lines.Bearing in mind the scarcity of decorated beads in the archaeological record and the singularity of the examples, due to their size and weight, they can be regarded as "special" objects possessing significant symbolism.
As such, it is reasonable to assume that although the raw material was relatively easily available throughout the communities that inhabited Iberia in the Copper Age, only the kin groups, factions or individuals who were buried in monumental tombs were able to afford the added value that allowed the production of such sophisticated objects as decorated fluorite beads.The coincidences between tomb 111 at Fuente Álamo and tomb 454 of El Argar (see Garrido-Cordero 2015), with high status young woman with rich grave goods including translucent beads, point to this consideration for the 2 nd millennium BCE, where high social differences are displayed.However, it is important to note that, paradoxically, most artifacts studied in this paper, particularly the decorated beads, cannot be ascribed to any particular individual due to the collective nature of the funerary records or the recording of the items in the late 19 th -early 20 th century of our era.

Figure 2 .
Figure 2. A sample of beads analyzed in this paper.

Figure 3 .
Figure 3. Raman spectra in the diagnostic region, left) set of samples that shows solely the fluorite diagnostic T 2g Raman band at c. 320 cm -1 , right) set of samples that shows the fluorite diagnostic T 2g Raman band at c. 320 cm -1 and additional bands at lower and higher frequencies.

Figure 4 .
Figure 4. Raman spectra in the frequency-shift region between 1000 and 2500 cm -1 showing the typical fluorite PL spectra.

Figure 5 .
Figure 5. Raman spectra in the frequency-shift region between 1000 and 2500 cm -1 showing the typical fluorite PL spectra lacking the T 2g Raman band.

Table 1 .
Inventory of fluorite items in Iberian late prehistory.