For quartz processing, the scattering effect of multiple laser beams can be used to distinguish a rock containing quartz from its identically colored neighbor. A pure or non-contaminated quartz rock will register as a glowing crystal, while a similar-looking piece of quartzite, sandstone or many other rock types with no quartz content, will simply remain dark and exhibit no visible scattering at all.
Conventional approaches have typically employed manual sorting or involved the deployment of color sorters. However, sorting which is based on color alone tends to reject rock material which, though it may be iron-stained on the surface, nevertheless still contains an acceptably low, and thus viable, percentage of iron. Rejecting such iron-stained material causes significant cumulative loss of yield, thus necessitating additional mining effort to maintain production levels. Also, as quarry material is gradually mined out, product specifications may become increasingly difficult to maintain as lower quality areas of the deposit are encountered.