[en] A fully portable source excited X-ray fluorescence analyzer has been developed to detect and quantify trace concentrations of gold in situ at the working face. The technique utilizes the 88 keV gamma-ray of ¹⁰⁹Cd to excite gold K/sub β$ X-rays which are detected and analyzed by the instrument. The instrument must meet two very tough criteria in addition to the normal laboratory specifications of a precision spectrometer. First, it must be able to withstand the rugged environment of a mine including high temperature, high humidity, dust, and bumps. Second, it must be fully portable and capable of being carried easily by an operator into this environment without impairing his ability to move around and work. 2 refs