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| Theory || Qualitative analysis || Quantitative analysis || Back-scattered and secondary electron imaging || Cathodoluminescence imaging |

The aim of qualitative analysis is to identify the material quickly without doing a detailed quantitative analysis that requires concentration measurements. The Energy Dispersive Spectrometer (EDS) in combination with a back-scattered electron (BE) detector is ideally suited for this purpose. Electron back-scattering is a function of the average atomic number of the specimen. Hence, a BE image efficiently distinguishes different phases in the sample (e.g., minerals in a rock) that cannot be distinguised easily in a conventional optical microscope image. For example, amphibole (amph) at the rim of clinopyroxene (cpx) cannot be easily recognized in the cross-polarized image below:

Once phase distinctions based on electron back-scattering properties are made, the elements in each phase can be easily identified by collecting an EDS X-ray spectrum with the beam positioned on the phase. The EDS spectrum below shows a typical hornblende (a common amphibole mineral) spectrum. The clinopyroxene spectrum is similar but it does not show the potassium peak and aluminum is usually lower.

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(Last Revised 11/29/2007 by Nilanjan Chatterjee)