A borehole was drilled in the early 1900's on the northwest bank of the Similkameen River, 2 kilometres southwest of Princeton.

The Blackmore Borehole No. 2 prospect is near the centre of the Princeton Basin, a northerly trending fault-bounded trough filled by Eocene volcanic rocks of mainly intermediate composition, comprising the Lower Volcanic Formation, and an overlying Eocene sedimentary sequence of sandstone, shale, waterlain rhyolite tephra (tuff) and coal, up to 2000 metres thick, comprising the Allenby Formation.

The drill hole intersected the upper two of four significant coal-bearing zones in a 530-metre section in the Allenby Formation (Princeton Group). The Gem-Bromley Vale zone, the lower of the two zones, was encountered at a vertical depth of 206.2 metres. The zone consists of a coal seam with a true thickness of 3.05 metres, including a band of dark shale, 15 centimetres thick. The seam is overlain by shale and sandy shale and underlain by shale. The aggregate thickness of clean coal is 2.90 metres (Paper 83-3, Figure 13B). This zone was mined at Bromley Vale Collieries (092HSE215) to the southwest, and the Gem mine (092HSE151), to the northeast.

The overlying Golden Glow zone was encountered at a vertical depth of 69.2 metres. The zone comprises a single seam of clean coal, 2.36 metres thick, overlain by shale, and underlain by sandstone (Paper 83-3, Figure 13B). The Golden Glow zone was also mined at Bromley Vale Collieries.