Outcrop of a classic layered pegmatite-aplite dike: the San Diego mine, Mesa Grande, San Diego County, California. In general, the pegmatite conforms to the "logo" pegmatite of Jahns & Burnham with a layered aplitic footwall and pegmatitic hangingwall. It differs from that model, however, in the fact that very coarse-grained microcline-quartz graphic intergrowths radiate upward from the footwall, not downward from the hangingwall as the model predicts.