X-ray diffraction (XRD) has been routinely employed in the Earth sciences to characterize the crystallography of rocks and minerals. Routine characterization of samples too small for analysis by classic automated powder diffraction methods becomes challenging without access to single crystal or micro-diffraction equipment. Here, we show that a traditional Gandolfi camera lined with an image-plate (IP) as the detection medium can return a fully quantitative diffraction pattern from a sub-milligram single grain specimen in a simple and straightforward manner. Data pertaining to peak positions (d-spacings) were assessed using SRM640c Si powder, while intensity data were compared to the certified values for intensity standard SRM676a alumina powder. The refined unit-cell dimension of Si powder differed from the certified value of 5.4312 Å by no more than 0.0003 Å with a standard deviation (σ) of 0.0002 Å among the three experiments. For intensity, the σ and disparity from the certified values of three diffraction experiments on SRM676a were both <2%. The results of a comparative study of the crystallographic parameters determined for a naturally occurring garnet and clinopyroxene given through the refinement of their crystal structure by single-crystal XRD method are presented. These show through Rietveld refinement of X-ray data obtained by the Gandolfi–IP method outlined here that both accurate and precise XRD data can be produced in a timely and cost-effective manner using only an IP, Gandolfi camera, and software freely available on the internet.
On experiences with an image-plate detector combined with a single-crystal diffractometer
