The following figures show ED spectra of various minerals, as recorded with a thin-window Si(Li) detector. The abscissae show the energy in keV. The accelerating voltage is 20 kV and the X-ray take-off angle is 30°. Only major (α) peaks of elements are labelled; the C K peak from the carbon coating is not shown. (Note that relative peak intensities vary with accelerating voltage and, in the low-energy region, are affected by the window characteristics.) Many minerals exhibit a considerable range of compositions, which should be taken into account.