01-22-2009, 10:31 PM
Quote:Matt,
I believe you are corret that orichalcum is not naturally occuring. I have personally analyzed roman "bronze" using x-ray fluorescence and the result was NO tin. The alloy had over 20% zinc and the remaining was copper. If there was anything else it was trace.
I've seen and done a lot of XRF analyses of artefacts that did have tin in them. The romans used a wide variety of cupric alloys (Sn, Pb, As, all are occuring components and not just as trace elements).
Also in some burial circumstances the tin can disappear from a cupric alloy by differential corrosion. What kind of XRF did you use? Portable XRF often gives very shady results... The problem with XRF is that there is no good supporting software for the analysis of ancient artefacts. As you probably know (but it might be interesting to people who don't know) the software has pre-programmed standards for modern alloys and it tries to find the modern alloy that corresponds best with the alloy that is analysed. If it can not find a similar alloy in the memory it will resort to giving values in between the measured alloy and the pre-programmed alloy that corresponds best (so this is not the real composition of the alloy you are analysing). You can 'train' the device by doing a lot of measurements and storing all the results but still it's almost impossible to get absolutely correct results.
About the roman brass (Cu and Zn) how do you suggest the romans made this then?
There is a lot of interesting information in Plinius' Naturalis Historiae, the book on non-precious metals.
Vale,
