A golden rule

New technique for processing fossils

Gondolella A 300-million-year-old tooth, from the extinct conodont Gondolella. This specimen, which is coated in gold, is the size of a pinhead (1.5 mm). Conodonts were small eel-like creatures with jaws unlike those of any modern animal. They died out about 200 million years ago. Image: David Jones and Mark Purnell, Univ. of Leicester
Picture of Mark Purnell, of University of Leicester's Department of Geology.
Mark Purnell

Picture of Andrew Abbott, of University of Leicester's Department of Chemistry.
Andrew Abbott

Oct 27, 2013 — Many objects are studied using the high power magnification of electron microscopes, but in order to study tiny fossils or microscopic details of larger fossils in this way, palaeontologists routinely coat the fossils with an ultra-thin layer of gold. So it is often necessary to remove the gold after analysis, which until now has been difficult and expensive, and moreover has required the use of dangerous chemicals like cyanide.

University of Leicester chemists are developing industrial electro-plating and polishing techniques using liquid salts called 'ionic liquids' which are safe, cheap and environmentally friendly. Recently scientists from the chemistry and geology departments there got together to see whether a similar process could be used on fossils.

They found ionic liquids can remove gold from fossils quickly and easily without damaging even tiny, delicate specimens. The liquids are safe to handle, can be simply disposed of and can even dissolve the gold without affecting the glue that holds the fossil specimen in place for analysis.

Professor Mark Purnell, from the Department of Geology, said: "There are many cases where collecting the evidence required for research affects fossils or other objects in ways that might be considered as somewhat destructive — gold coating for electron microscopy falls into this category. Understandably, this creates problems for places like museums which have to balance the value of research on their collections against the risk that specimens will be affected. This approach to gold removal offers a new way of tackling this problem that is safe for both researchers and the specimens."

Professor Andy Abbott, from the Department of Chemistry, added: "This is a very nice demonstration of the use of ionic liquids for metal recovery but it is just the tip of the iceberg as we are using this technology for the recycling of a wide range of alloys and waste materials."


Details of the new technique were published in the journal Palaeontologia electronica.

Based on materials obtained from the AAAS

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