Abstract: A method and apparatus for detecting impurities in quartz sand. The apparatus comprises at least one light source; at least one light detector assembly; a transport device; and a signal processor that receives the at least one signal from the at least one light detector assembly. The method comprises moving the quartz sand; illuminating the quartz sand to excite luminescence emission from impurities; receiving luminescence emission from the impurity; generating at least one signal indicative of the excited luminescence emission from the impurity; and determining if the signal represents an impurity in quartz sand.