The Greendrop Lake showing is located near a small creek on the northwest side of Greendrop Lake.

The area is underlain by granodiorite and quartz diorite of the Oligocene Chilliwack Batholith. These have intruded the Custer Gneiss, which occurs to the north and east of the occurrence, and Eocene conglomerates and sandstones, which occur to the west. The Custer Gneiss is a metamorphic complex derived mainly from lower Mesozoic and possibly Paleozoic and Precambrian rocks, and metamorphosed in the Late Cretaceous or early Tertiary.

The occurrence is reported by Cairnes to be very similar to the Elk Horn (MINFILE 09HSW078). It is, therefore, assumed that galena, sphalerite and pyrite occur in calcite and quartz stringers and veins in a fracture zone in the Custer Gneiss (GSC Summary Report 1923 Part A, pages 70, 71). Lime silicate rock (skarn?) is closely associated with the granite gneiss host, which contains clinopyroxene (diopside?) and epidote.

In 1979 and 1980, programs of prospecting and geological mapping were completed on the area as the Greendrop property.