The Tulameen showing is situated on the east bank of the Tulameen River, 9 kilometres west-northwest of Princeton.

A small elongate stock of coarse-grained granodiorite and quartz diorite intrudes andesitic tuff and agglomerate, with minor rhyolite and porphyritic andesite, of the Upper Triassic Nicola Group. The stock trends northward for 380 metres and is up to 100 metres wide.

The volcanics show moderate to strong argillic alteration, while the stock exhibits minor chlorite and epidote alteration.

Sparse chalcopyrite and pyrite occur in quartz veins and irregular shears in the intrusive and volcanics, and as disseminations in andesitic tuffs, in the vicinity of the south end of the stock.