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2000 Mineralogical Society Schlumberger Medal

	Presentation by the President, Dr David Morgan, to Dr Paul Nadeau, at the Annual Winter Conference Dinner, 4 January 2001

 
The Schlumberger Medal recognizes scientific excellence in mineralogy and its applications. It is my great pleasure to present this to you tonight, Dr Paul Nadeau, for your contributions to clay mineralogy of which the most significant has been the proposal that interstratified clay minerals are composed of nano-crystalline ‘fundamental particles’ whose absorptive interfaces are responsible for the expanding smectite layers observed by X-ray diffraction. This model has not been without opposition, but the debate it generated has inspired other mineralogists to seek alternative explanations, which in themselves have advanced our knowledge of clay mineral genesis.

Following your first degree at Boston College in 1975, where you were inspired by the teaching of C.S. Hurlbut, you moved to Dartmouth College to study first for an MA and then a PhD. Your PhD dissertation was on bentonites in Cretaceous marine sediments in the western interior of North America and their involvement in tectonic and igneous activity. Here, you worked with Bob Reynolds, and started to question the accepted mechanism by which smectite is converted to illite with increasing depth and temperature. You were not convinced that potassium fixation and smectite layer collapse was the answer, but it was not until 1982, when you moved across the pond to the Macaulay Institute in Aberdeen, that you were able to develop another quite radical hypothesis.

At the Macaulay, when you were characterizing bentonites with high illite:smectite ratios using transmission electron microscopy, you kept observing particles that were much thinner than the ‘MacEwan crystallites’ on which current interpretation of XRD of interstratified clays was based. By quantitatively measuring thickness, area and perimeter distributions of these extremely thin particles, and by further laborious experimentation involving mixtures of these clays and ‘pure’ smectite dispersions, you were able to reconcile TEM observations and XRD results under the concepts . . . [Full Text of this Article]