The old Thistle adit is located at the base of a line of cliffs about 1.6 kilometres northeast of the summit of Mt. Hayes. The adit lies within Saanich granodiorite of the Jurassic to Tertiary Coast Plutonic Complex which intrudes Upper Cretaceous Nanaimo Group sedi- ments comprised of shale, sandstone and conglomerate.

The showing consists of a mineralized vein, traceable over 31 metres and from 5 to 305 centimetres wide hosted in granodiorite. The vein is coarsely crystalline, composed mainly of quartz irregu- larly intergrown with feldspar and minor mica. This vein is reported to host up to 10 per cent chalcopyrite, bornite and molybdenite. Development consists of two short adits connected by a short inclined level and a stope.