Advances in geophysical technology and computer imaging now permit mapping of geologic features at various depths beneath the Earth's surface in more detail than ever before. Geophysical methods, which for some years have been used to explore for diamonds (and many other minerals), also hold promise as important tools in both exploration for new colored stone deposits and assessment of known deposits. Particularly exciting are the use of seismic-reflection and radar-imaging techniques for high-resolution mapping of near-surface pegmatites, veins, metamorphic layering in crystalline rocks, and alluvial deposits in sedimentary rocks. These techniques can produce images of regions only a few centimeters to a few meters in size down to several meters to tens of meters below the surface. Thus, it is now possible to locate directly some buried structures containing gem deposits.

Appears on pages 4-23

Photo Harold and Erica Van Pelt