The first of these tunjos (no.7) has a relatively high gold content and low copper contento In this case the compositional difference between the surface analysis and analysis of metal at the centre of the casting is a few percent. The surface analysis of the tumbaga (copper-rich gold alloy) tunjo (no. 1) is so different from the value for the core metal that it gives a completely false picture of the quantity of copper in the original casting alloy. To allow comparison of like with like it is therefore important when publishing analytical results to state how the analysis was done and on what part of the object and it has to be emphasised that surface analysis is worse than useless, it is positively misleading.
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Photograph 3: Muisca cast necklace pendants (length of largest, 1.27 cm) [photo A. Milton, British Museum] |
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Photograph 4: Detail of tunjo 7 (height 4.8 cm) [photo S. La Niece, British Museum]. |
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Photograph 5: Detail of tunjo 1 (heigth 5.5 cm). [photo S. La Niece, British Museum]. |
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Photograph 6: SEM micrograph of a polished section through the broken tip of tunjo 7. Note the continuity of the cast structure between the base plate of the tunjo, running horizontally across the bottom of the photograph, and the round sectioned "wire" on top of it. (BSE image. Width of section 1.2 mm) [photo S. La Niece, British] |