The region is underlain by (?)Hadrynian to Paleozoic Snowshoe Group rocks. The Snowshoe Group is an assemblage of dominantly metasedimentary rocks within the Barkerville Terrane of south-central British Columbia. The metasedimentary rocks consist primarily of marble, quartzite and phyllite. In the Yanks Peak area these rocks comprise the Keithley and Harveys Ridge successions, but further to the east they remain undifferentiated. Metamorphism of the region varies from chlorite to sillimanite and higher grade. Gold-bearing quartz veins occur only in greenschist facies rocks.
The Jim showing consists of several mineralized quartz-ankerite veins, up to 1.8 metres wide, hosted by dark grey argillaceous quartzite. The hostrocks are folded about northwest trending axes and the veins commonly strike northeast and east. Mineralization consists of sparsely distributed galena, sphalerite, pyrite and gold.
An average of sampling over 14.5 metres of the A1 trench in 1978 assayed 71.60 grams per tonne silver, 3.6 per cent lead and 2.38 per cent zinc (Assessment Report 7106). A selected grab sample containing 75 per cent pyrite taken from the Jim vein in 1954 assayed 78.80 grams per tonne gold and 10.28 grams per tonne silver. Gold values are higher with higher amounts of pyrite (Bulletin 34, page 68).
The Jim adit was started in 1946 to explore the Jim vein zone at depth. The portal is about 97 metres south of the northwest corner of the Ridge No. 4 claim (Lot 4681). The elevation of the portal is 1718 metres, and that of the vein outcrops ranges from 1728 to 1765 metres. The adit was driven at 033 degrees for 32 metres, where it is crossed by a northerly striking fault. One branch 12 metres long was driven northward along the west side of the fault, and another 28 metres long was started on the east side of the fault but crossed back to the west side near the face of the drive. The northerly striking fault is exposed in two places underground as a gouge zone 0.6 to 1.2 metres wide. It has a strike of 352 degrees and a steep westerly dip. The amount and relative direction of movement are not known. All the veins underground, of which there are many, strike northeastward (about 070 degrees) and dip steeply southward. They range in width from a few centimetres up to 76 centimetres, but most are less than 30 centimetres wide. Surface stripping in the northwest corner of the Ridge No. 4 claim and in the southeast corner of the Jim claim has exposed a large number of veins which lie in a zone about 152 metres long and 61 metres wide and whose general trend is a few degrees west of north. Several northerly striking faults, which offset the veins about a metre, are seen in the open cuts. Two veins about 91 metres northeast of the Jim adit are cut by steeply dipping faults striking 070 degrees, on which the movement is very small. Striations on the fault planes plunge 70 degrees west.
In 1954, three Crown-granted claims, Jim (Lot 11237), Pete (Lot 11238), and Ridge No. 4 (Lot 4681), and the Crystal group of recorded claims adjoining them on the north, were held by Lieut.-Col. F.H.M. Codville, of Duncan.
