Hi Jeff and all,
Sorry I'm late to the discussion, but I'm not convinced that a microprobe would give a good answer to the percent of meteoric iron in a keris, especially an old one.
The unobvious problem is that keris blades are occasionally cleaned with an arsenic (As) solution, so the researcher has to factor in the accumulation (if any) from cleaning. Since it's not pure arsenic in the Indonesian cleaning solutions, this would take some experimentation.
The obvious problem is that the terrestrial iron isn't pure iron, nor is the carbon to make the steel pure carbon. There's going to be a mix of other trace elements that will have to be factored in. In old blades, the iron will not be to an industrial spec, but may have been smelted from ore in the village where the blade was made, or beaten together from recycled sources. Similarly,the carbon source can affect the trace element signature of the steel. For instance, coal picks up various heavy metals (such as mercury, the bane of the midwest US), and trees that are used to make charcoal typically accumulate some cesium (a byproduct of potassium metabolism), and some plants deliberately accumulate metals. As another example, one tree species in New Caledonia naturally accumulates so much nickel (as a chemical defense against herbivores) that the sap could be mined, if it was more common. Given that, in Indonesia, we're talking about one of the richest rainforest areas on the planet (i.e. lots of tree species), the tree species used into charcoal could affect the chemistry of the charcoal used to make the steel, affecting the chemical fingerprint of the resulting keris.
Complex? Yup. The only solution I've come up with so far is to get two blades from the smith, one a tool with no meteoric iron, the other a keris with some putative meteoric iron, both forged at roughly the same time, so they have the same source materials, aside from the meteoritic component. Then you can factor out the terrestrial sources. After that, you have to determine how cleaning the keris with the arsenic solution affects that blade's chemistry. Once you've done that, you can actually say how much of the keris is meteoric.
Bottom line, it will be difficult to predict or determine the trace element chemistry of the terrestrial component of keris, and without that information, it would be very, very difficult to detect the extraterrestrial material in a trace element analysis.
The "good" news is that an old keris is in many ways the worst case scenario. A blade forged with modern, industrial steel, made in the northern hemisphere from materials of known or knowable chemistry, would be much simpler to study
F
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