The Yankee Girl is underlain by greenstone of the Devonian to Permian Knob Hill Group which is intruded by small granodiorite bodies, probably of the Jurassic to Cretaceous Nelson Intrusions.

Workings consisting of deep shafts and pits are still evident on the property. Quartz veins are associated with shear zones in the greenstone. The greenstone is heavily fractured and sheared. The wall rocks were typically pyritic and very silicious and intruded by numerous quartz veinlets. On surface, the shear/vein zones are very irregular, pinching and swelling along strike. Dips also varied in direction. Chalcopyrite, malachite, galena and pyrite occur as stringers and disseminations in the quartz veins that trend in a northeast to easterly direction with dip to the northwest.

The history of the Yankee Girl/Yankee Boy goes back to before 1900. During 1900, the Yankee Boy was the only mine reported to have shipped ore from the camp. In 1905 considerable development work was undertaken. No recorded work was done on the property between 1905 and 1924. Seventeen tons were reported shipped in 1925 with values of $40 to $78 of gold and silver per ton. The 1925 Minister of Mines Annual Report describes the mineralized zone in the upper level of the old workings as a vein varying in width from 5 to 40 centimetres wide and carrying pyrite, galena, sphalerite, gold and silver in a gangue of quartz.

Underground development continued through to 1936. Shipments of ore to the Trail smelter were made in 1926 (11 tons), 1930 (21 tons), 1934 and 1936. A total of 389 tons was shipped in 1936, yielding 460 oz of gold and 382 ounces of silver (Minister of Mines Annual Report 1936).

By 1936, when operations were suspended, considerable work consisting of numerous opencuts, surface trenching and underground development consisting 2 main levels, 2 intermediate levels as well as winze, raise and stopes had been completed Most of the development was conducted on the Yankee Boy Crown grant.

In 1982, a flagged grid was established on the Yankee Girl Crown grant and soil samples were taken. In 1983, Monashee Geological Services conducted a soil geochemical survey on a 1982 soil anomaly. The 1983 survey included a ground VLF survey over 1.5 kilometres in length. In 1988, Redding Gold conducted a 5.4 kilometre VLF survey, a 6.2 kilometre ground magnetometer survey and collected 24 rock samples.