Mr. President, members of the Executive and Council, Members of the Association, and Guests: I am pleased to accept the Peacock Medal. This is a recognition of not only my own scientific efforts and accomplishments, but also of those who trained me, and the students who have chosen to work with me over the years. I am a mineralogist because Lowell Trembath gave me an opportunity to do research during the summers of my undergraduate years at the University of New Brunswick. Michael Fleet at the University of Western Ontario supervised my master's work on ordering in synthetic feldspars. Frank Hawthorne, my PhD advisor at the University of Manitoba, gave me complete freedom to explore computation chemistry, synthetic chemistry, and mineral crystal structures. I studied phase transitions in minerals with Michael Carpenter at Cambridge University, and then worked in Rod Ewing's group at the University of New Mexico, which is where I began my emphasis on uranium mineralogy.
In 1996 I was teaching at the University of Illinois and the chemistry department there had a new X-ray diffractometer with a revolutionary CCD-based detector. I applied this to several uranium minerals there and dreamed of its broader use in mineralogy. The University of Notre Dame funded my dream in 1997 by purchasing a single-crystal diffractometer for my sole use, and I have been there ever since. First I focused on the structures and stabilities of uranyl minerals, and over time I broadened my efforts to include uranium synthetic compounds, and eventually neptunium and plutonium chemistry. In 2010 the University of Notre Dame invested in my dreams again with the construction of new actinide synthetic laboratories, and the United States Department of Energy has funded my work, and that of my students, since 1997. In 2014 I donated that original X-ray diffractometer to Juniata College in Pennsylvania, where it is used for teaching crystallography.
In 2002 I became fascinated by a peculiar uranyl mineral known as studtite because it was reported to contain peroxide, and because it grew on spent nuclear fuel contacting water, as well as on the radioactive debris of the Chernobyl reactor. We solved its structure using materials from the Belgium Museum of Natural History, and showed that the peroxide was generated by the interaction of radioactivity with water. Then a strange thing happened. In 2004 Karrie-Ann, a PhD student of mine, found a book published in the Soviet Union - behind the iron curtain - in the 1960s that somehow had been translated into English and re-published by an Israeli press, and it happened to be in the library at Notre Dame. It was a book about synthetic uranium compounds, and there was a whole chapter on uranyl peroxide crystals formed from alkaline solutions. I repeated the experiments, which were described in great detail in the book, and Karrie-Ann and I used the revolutionary diffractometer mentioned earlier to solve the structures. That is how we discovered that uranyl peroxide polyhedra self-assemble in water to form a vast family of nanoscale cage clusters a family that we have now developed to about 120 members.
Discovery of the clusters in 2005 proved to be a major distraction from my mineralogical studies, but it did allow for the funding of lots of graduate students and post-docs in actinide chemistry in my group. Our cluster work continues today, but I am also moving back towards my research roots in mineralogy. We have described several new uranium minerals over the past couple of years, including a fascinating uranyl carbonate that contains the first natural uranyl cage cluster that will be named ewingite, after Rod Ewing, who gave me that chance to study uranium mineralogy 20 years ago. We have lots of interesting work underway focused on the thermodynamics of uranyl minerals as well.
Finally, I want to express some thanks. The Mineralogical Association of Canada, of which I became a student member in 1986 and have been active in since, has done a great deal for the mineralogical sciences in Canada and internationally. The Canadian Mineralogist published my top-three most highly cited papers, and Bob Martin edited dozens of them - thank you Bob. I thank my wife Tammy and my children, who always support me. I thank each of my mentors that I mentioned earlier, and all of my teachers over the years. I thank Ginger Sigmon, who has managed my research group for seven years. I thank all of the superb graduate students and post-doctoral researchers who have done the real work. And finally, I thank all of you for this great honour.
Peter C. Burns