The area of the North Star prospect is underlain by basalt and massive to locally bedded chert of the Permian to Jurassic Hozameen Complex. Basalt-chert contacts are steeply dipping and probably faulted. Small intrusions of diorite to granodiorite of unknown, but probable Tertiary age occur in the basalt. A fault striking 015 degrees along Pyrrhotite Creek truncates a 120 degree striking fault that passes through the Giant Creek area. Monger has mapped another west-northwest striking fault in the valley north of the property (GSC Map 12-1969).
Over several square kilometres, the basalt is altered and veined. Alteration consists mainly of silicification and lesser sericitization. Three main types of mineralization are reported to occur in the vicinity; these include skarn, veins and porphyry types.
A number of showings are included under the North Star name, all found in the vicinity of where the two main forks of Star Group Creek join, at 1350 metres elevation. Descriptions of the two most significant zones near this locale are found in Assessment Report 8839 and are summarized as follows.
The Earl showing, about 240 metres up the west fork of Star Group Creek, is a massive sulphide skarn exposed over a width of 2 metres. It contains pyrrhotite, lesser sphalerite and minor chalcopyrite, the latter mainly associated with patches of strongly silicified basalt. Just to the south of the skarn is a vein and silicified breccia zone containing massive sulphide veins up to 30 centimetres wide. The main vein, 10 to 20 centimetres wide, grades upwards from pyrrhotite-rich at the base to coarse-grained sphalerite with lesser chalcopyrite near the top. Nearby is a 3 centimetre wide vein composed of massive arsenopyrite and quartz. Farther south, scattered veins (a few millimetres wide) containing pyrrhotite and sphalerite with calcite and quartz are found. Still farther south, a limestone layer in the basalt occurs, along which has developed a skarn composed of calcite, pyrrhotite and sphalerite with patches of vuggy quartz, epidote and actinolite. South of the Earl zone, between the two branch creeks, on what is called Gold Pan Point, is a body of granodiorite.
A 1961 diamond-drill hole on the Earl zone (as quoted in Assessment Report 8839) intersected 3.7 metres grading 10.28 grams per tonne gold, 14.06 grams per tonne silver, 1.0 per cent zinc, 0.10 per cent copper and 0.06 per cent lead. Gold is reported to be present with some skarns and absent in others. One of the best gold assays from 1980 came from an unmineralized shear zone in basalt.
The Western showing, formerly called the "Glory Hole", is located about 80 metres east of the where the two forks of Star Group Creek join. It consists of four skarn zones over a north-south distance of 40 metres. The skarns typically are made up of pyrrhotite, quartz and sphalerite. One of the zones contains subzones of arsenopyrite and quartz, and one of quartz with minor pyrrhotite and pyrite. The largest of the four skarn zones is 5 metres long and 3 metres wide. Adjacent to it is a 1 metre thick lens of marble. Surrounding the skarn and marble is a porphyritic basalt, and nearby is a porphyritic dacite-rhyolite intrusion. The skarn appears to strike 040 degrees and dip 50 degrees southwest under the limestone-marble. A sample taken over 7.6 metres from an opencut yielded 2.07 grams per tonne gold, 53.14 grams per tonne silver, 5.95 per cent zinc, 0.15 per cent copper and a trace of lead (Assessment Report 8839 (quoting a previous study)). Sargent reported that by 1938 there were 4 cuts and a 7.6 metre adit on this zone (Minister of Mines Annual Report 1938, page F18). The zone was also reported to have been drilled in 1961.
In 1923, Cairnes reported a body of ore occurring in the area of granodiorite on Gold Pan Point which was comprised of a considerable proportion of galena and arsenopyrite, as well as sphalerite and pyrrhotite (GSC Summary Report 1923, page 75). Samples taken at that time yielded as much as 788 grams per tonne silver.
