The TA-Greendrop occurrence is located 650 metres south-southeast of Greendrop Lake, at an elevation of approximately 1040 metres.

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 intrusive rocks have been altered and pyritized by later intrusions of a quartz diorite porphyry and a breccia complex. Dikes and sill-like igneous bodies of various compositions have subsequently been emplaced. A centrally located elliptical gossan zone is associated with multiple intrusions of mainly dioritic composition. Hydrothermal alteration in the gossan zone is characterized by a variable assemblage of quartz, sericite, chlorite, carbonate, epidote and minor biotite. Essentially two alteration suites are recognized, phyllic and propylitic.

Primary mineralization in the gossan area includes pyrite and minor chalcopyrite, molybdenite, magnetite, sphalerite and galena. Quartz, sericite, calcite and gypsum are reported to be the main non-metallic hydrothermal minerals. Pyrite occurs in fractures and disseminations and as coarse clusters with quartz and rare molybdenite in a rubble breccia. Molybdenite also occurs within an intensely altered quartz stockwork along its contact or in steeply dipping quartz veins. Chalcopyrite is found in fracture veining and minor disseminations within adjacent wallrock. Sphalerite and galena are common in drill core but appear restricted to steeply dipping quartz-calcite veinlets. Several specks of coarse scheelite were also identified in drill core. Magnetite is abundant in altered granodiorite near the western contact of the rubble breccia.

In 1980, a diamond drill hole (DH #1) yielded up to 0.3 per cent copper over 1.8 metres; while another section, lower down the hole, yielded 0.21 per cent copper, 13.4 grams per tonne silver and 0.125 gram per tonne gold over 1.2 metres. Another drill hole (DH #2), located approximately 300 metres to the northwest, yielded up to 0.07 per cent molybdenum over 3 metres (Assessment Report 8376).

Other occurrences reported in the area include a gold occurrence, as indicated on GSC Map 737A, and another molybdenum occurrence on the ridge to the west as reported in Assessment Report 8376.

In 1979 and 1980, programs of prospecting, geological mapping and two diamond drill holes, totalling 921.1 metres, were completed on the area as the Greendrop property.