The electron microprobe provides detailed information on the chemical composition of minerals.
This is achieved by focusing a beam of electrons onto the surface of a mineral. X-rays are produced where their wavelengths or energies are characteristic of the elements in the mineral.
The Department of Mineralogy has two electron microprobes used by trained staff within the Mineralogy and other Science departments. Both instruments are available to external organisations.
Cameca SX50 electron microprobe
This is a dedicated microprobe capable of unattended overnight operation.
The Cameca SX50 is a dedicated wavelength dispersive electron microprobe. Excellent qualitative or quantitative determination of elements can be obtained on elements with an atomic number greater than five (boron) to detectable limits in the order of 0.01per cent. The process is non-destructive, however, the minerals have to be in the form of a polished section. The instrument is controlled by a Sun work station and is networked within the Museum to allow scientific staff ready access to their data. The instrument can be pre-programmed to operate unattended at night and weekends.
Hitachi S2500 / Link AN10000 scanning electron microscope
A scanning electron microscope with analysis attached for qualitative analysis.
This is an Hitachi S2500 scanning electron microscope with a Link AN10000 energy dispersive X-ray microanalysis attachment. The instrument has a large specimen chamber and is capable of qualitative or quantitative analysis of elements with an atomic number greater than 11 (sodium). The detection limits are in the order of 0.2 per cent. The process is non-destructive and qualitative information can be gained from rare or unique specimens taken directly from the mineral collections.
Current research
Some of the reseach using the electron microprobes:
The electron micrograph on the right shows a precipitation of the mineral malachite ( a hydrated copper carbonate). This work comes within the Museum's Environmental Quality Programme and forms part of the chemistry and precipitation of minerals from mine waters at the Geevor tin mine in Cornwall, England.
