A variety of crystals may be found here. Crystals occur near Saltville in dark limy shales and shaly limestone layers above the post-Knox unconformity. An unconformity is a gap in the rock record, when either no deposits occurred, or there was erosion. Roughly 450 million years ago, the state of Virginia was under a body of water known as the "Sauk Sea". The Knox Unconformity occurred when the Sauk sea level fell dramatically. As the sea water drained off of the Virginia landscape, sedimentary rocks became exposed and began to erode. In Virginia, the Knox Unconformity is not consistent and sometimes barely exists, mostly in low areas that probably remained underwater when the sea fell to its lowest level.

Most of these amazing Saltville crystals are found in light colored soil material formed from rock weathering in place, but they are also found in vugs or seams in un-weathered bedrock. A surprising variety of crystal morphologies (crystal shapes) can be found. They are uniquely distinct from Tennessee crystals due to this variety being formed in a post-unconformity setting. Habits include both prismatic and bi-pyramidal doubly-terminated crystals occurring side by side, many with small "capping" crystals at both ends.

Tectonically, these crystals are in the Saltville thrust sheet above the Saltville Fault which comes to the surface over two miles to the northwest. That area is historically known for its salt seeps, brine wells, and gypsum mining. Halite (rock salt) and gypsum occur at depth below the fault and were heavily involved in the Saltville Fault earthquake shearing and deformation. The history of shearing and deformation is complex. These tension gash fractures are found in local bedrock. They are small and narrow, but larger ones weathered to produce the residual soils.

Internal carbonaceous phantoms are common and suggest an early stage of equant stubby crystals (crystals of nearly equal dimensions) of simple morphology. Their precise shape and outlines are indistinct, as the black central area is defined by the presence of large irregular inclusions as much as a defined crystal shape. No fluorescence from petroleum is visible under a low power microscope. This sequence is in contrast to the "bi-pyramidal over prismatic" growth commonly observed in crystals in Tennessee, where overgrowths, and crystals from the Sevier Shale thought to be of later origin, are more commonly bipyramidal. Re-healing of broken surfaces can also be observed in some specimens, suggesting that growth took place during deformation of the surrounding rock. Most crystal faces are complex, with mirror-like faces the exception.

These unique crystals are often referred to as "Saltville Quartz", "Saltville Diamonds" or "Virginia Knobby Quartz"