Professor Dave Prior
For us to be able to look at the samples we’ve collected from the drill core using microscopes, we need to prepare it so that we can look through it using light, and also we can look at the surface in great detail using scanning electron microscopy and electron back scatter diffraction. So to see through it using light it needs to be thin, so the process is to use diamond-coated saws to cut out a small chip of the rock about a centimetre thick or so. And we grind flat one side of that and stick it to a piece of glass, then cut off most of the chip so we have a piece of rock of say a millimetre or so thick, and then we grind that gradually to make it thinner and thinner, and we use a microscope to assess how thick it is, to check until we get exactly the right thickness. And then from there, we clean up and polish up the surface. And so then we have a sample which is in fact 30 microns thick – 30 microns is really good for transmitted light polarised microscopy so we can see lots of distinctive features in the minerals, and we can see the microstructures, and the polished surfaces enable us to get really good quality images in the scanning electron microscope.
Professor David Prior, Dr Virginia Toy and Brent Pooley, Department of Geology, University of Otago.