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Understanding Caribbean Jadeitite Exchange Networks pre- and post the arrival of Columbus

Ever since the first colonization of the Caribbean islands 6000 years ago, rocks or “lithics” as we call them were used to manufacture a wide range of objects. These ranged from special and likely highly valued objects like figurines, ritual items and jewellery to more utilitarian items like axes, hammerstones and other tools. Throughout pre-colonial times a high diversity of lithics were utilised within the Caribbean islands, which ranged from rocks formed in volcanoes or those laid down as sediments in ancient lakes and seas to metamorphic rocks that had been subjected to heat and pressure in the ancient past, such as the jadeitite in figure 1.

Fig.1: Macroscopical comparison of a jadeitite axe and a potential jadeitite source rock, both from the Dominican Republic. The key point about some of the lithics used in the manufacture of artefacts is their distribution across the Caribbean.

Tracking Rocks

The key point about some of the lithics  used in the manufacture of artefacts is their distribution across the Caribbean. Certain rock artefacts can be found throughout the Caribbean even though their sources are restricted to small regions on a limited number  of islands.  This tells us that lithic items have been exchanged and transported over distances that vary from 100m, the “producers” who lived close to a source to 100’s km, the “consumers” at the far end of the exchange network.

Since rocks do not move across the sea by themselves, tracking the movements of lithic raw materials and objects across the Caribbean will give us more insight into social networks. This knowledge can then be used to better understand the great changes in indigenous societies following the arrival of Columbus; across the historical divide. Before we are able to track the redistribution of (certain) lithics between the islands, let alone re-construct exchange networks, the geology of the entire region must be fully understood.

Metamorphic Complexes in the Greater Antilles

Ongoing work is designed to characterise the mineralogy, trace element and isotopic compositions of the metamorphic complexes in the Greater Antilles that served as the source of lithic materials. The results provide the database with which to determine artefact provenance. A special emphasis is being placed on the geochemical characterisation of jadeite rocks which were frequently used for producing axes that were transported throughout the Caribbean. Today jade remains a highly prized material that is used widely in delicately carved artwork. In the past it was its hardness that was highly prized but some complex carved artefacts were also produced.

Jadeitites are formed where tectonic plates collide and one plate is pushed under the other. The high pressure and moderate temperatures leads to jade formation by precipitation from sodium-aluminium-rich hydrous fluids (Fig. 2). The exact conditions under which the jade is formed leads to subtle compositional differences that are utilised to distinguish between different source regions.

Fig.2: left: jadeite originated by precipitation in a blueshist vein, and right: jadeite generated by the replacement of a parent rock.Worldwide, jadeite sources are limited. In the circum-Caribbean jadeite can be found along a former plate boundary in Guatemala, eastern Cuba and the northern Dominican Republic (Fig.3).
Fig.3: Sketch displaying tectonic plates and plate boundaries of the Caribbean. Red circles indicate jadeitite sources which occur along an inactive subduction zone.

Current Work of the VU Team

The strategy of the VU team is to optimise essentially non-destructive laser sampling methods and integrate them with state-of-the-art analytical techniques to determine strontium, neodymium and lead isotopes on sub nanogram amounts of material. Coupled with simultaneous compositional analysis, this will allow us to discriminate where the jade is from. Current work is focused on the optimization of a prototype portable laser device (Fig.4) that has been modified to sample lithic artefacts (demonstration video) at museums, the samples of which can then be taken back to the laboratories of the Vrije Universiteit of Amsterdam for geochemical analyses.

In future Hot Topic posts we will explain more about the importance of the laser-based non-destructive sampling techniques and how this is allowing us to sample precious museum objects as well as update you on the lithics networks we have been uncovering.

By Alice Knaf

Fig.4: A) Assembled portable laser ablation sampling device and B) details of the laser ablation module; from Glaus et al., 2012. 
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