Automated gold search and applications in process mineralogy

An image-analysis program written at CANMET performs an automated search fo r precious minerals. The program can search, for example, for gold minerals in polished sections. The search involves a meander of approximately 100 x 100 fields (back-scattered electron images) at a magnification of x400, wh ich allows gold grains as small as 1 mu m in diameter to be detected. Typic ally, an overnight search of a -45-mu m product will scan ca 1 500 000 part icles, providing data that are not easily obtained through manual operation of an optical microscope. The program follows the sequence: location of gr ains of correct brightness; acquisition of gold X-rays (AuLalpha) from such grains by wavelength-dispersive spectrometry; filtering to remove artefact s; and recording of the images and stage location for subsequent retrieval. At the end of the run the program allows the operator to verify and identi fy the grains so found. The approach has already been applied in many studi es of gold ores for commercial clients and three case histories are describ ed.