Gold and Fossils: Chemists Find New Solution

British scientists have developed a harmless, straightforward and inexpensive technique for removing gold from fossils.

Image shows a 300 million year old Gondolella gilded for the scanning electron microscopy (David Jones / Mark Purnell / University of Leicester)

Fossils can reveal a huge amount of scientific information when studied using the high power magnification of electron microscopes, but in order to study them in this way, paleontologists routinely coat the fossils with an ultra-thin layer of gold.

This obviously changes the way the fossil looks, and so it is often necessary to remove the gold after analysis, but this is difficult and expensive and uses dangerous chemicals like cyanide.

Chemists at the University of Leicester are developing industrial electro-plating and polishing techniques using liquid salts called ‘ionic liquids’ which are safe, cheap and environmentally friendly.

They found that ionic liquids can remove gold quickly and easily without damaging even tiny, delicate fossils. 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. Their findings appear in the journal Palaeontologia electronica.

“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,” said Prof Mark Purnell of the University of Leicester’s Department of Geology, a co-author of the paper describing the new technique.

“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,” he explained.

“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. The University of Leicester is building a strong reputation for the development of sustainable materials,” concluded Prof Andy Abbott of the University of Leicester’s Department of Chemistry.